Compounds: One word, two words, or hyphenated?

Prefixes vs. Compound Words

Prefixes

Usually can’t stand alone as words, with a few exceptions.
Examples: anti-, dis-, pro-, re-.

When they are in the dictionary, they are usually one word: prehistory

CMS says if not in MW11 dictionary, make it one word. preclean
AP says if not in WNW dictionary, hyphenate it. pre-clean

This post discusses compound words only. For more about prefixes, see separate post: Prefixes: One Word or Hyphenated?

Compound words

Both words can stand alone as words. They can be one word, two+ words, or hyphenated.
Examples: dollhouse, book club, half-truth.

Both CMS and AP say if it’s not in the dictionary, make it two words:

an open book

But hyphenate if you’re using it as an adjective before a noun:

an open-book test, the nice-looking shoes, the low-quality carpet.

If it’s after a noun, or is a noun itself, it’s two words:

I work full time.

The shoes, low quality but nice looking, are my favorite.

I am an open book. (noun)

If it’s an adjective after a be verb, CMS says leave it open, but AP says to hyphenate:

The test was open book. (CMS)

The test was open-book (AP)

With a hyphenated compound:

high-end-style bags = high-end + -style

game show–style format = game show + -style (CMS uses an en dash, AP uses a hyphen)

You will also hear these terms, but I’ll use “one word” and “two words” for clarity to a broader audience:

closed compound = one word: dollhouse
open compound = two words: book club
hyphenated compound = hyphenated: half-truth

Compound terms: one word, two words, or hyphenated?

1. Check MW11 dictionary (for Chicago style, 7.85) or WNW dictionary (for AP style, under hyphen).

2. If it’s not there, it’s either two words or hyphenated. (7.85)

3. Does it include an -ly adverb? If yes, it’s two words. (CMS 7.85 p. 377, AP under hyphen)

poorly trained employees.
They were poorly trained.

4.
For CMS, does it include more, most, less, least, or very? If yes, it’s two words, unless it causes ambiguity. (7.85, p. 377)

For AP, does it include very? If yes, it’s two words. (The other terms are not mentioned.) (AP under hyphen)

the more popular option
the most popular option
the less expensive item,
the least expensive item
the very happy child

Examples of ambiguity.

We have more experienced employees than any other company. (More modifies experienced employees, meaning “a higher number of experienced employees.” Might be better to rewrite the sentence to avoid misreading.)
The more-experienced employees will be promoted. (More-experienced modifies employees, meaning “the employees with more experience.”)

5. Is it a proper name? If yes, it’s two words. (5.91) (AP does not weigh in on this topic, but would likely agree.)

a Christmas Day miracle
her Second City training

6.
Are you using it as an adjective before a noun? Then use a hyphen.

For CMS, are you using it as an adjective (or adverb) after a noun? Or as a noun itself? Then keep it two words. (CMS 5.81, 5.99, 7.85)

For AP, same rules EXCEPT is it an adjective after a be verb? Then hyphenate it. (AP under hyphen)
(be verbs = is am are was were be being been)

the well-traveled student.
The student was well traveled. (CMS) The student was well-traveled. (AP)

a high-level skill, a higher-level skill
My skills were at a high level. My skills were at a higher level. (noun)
My skills are high level. (CMS) My skills are high-level. (AP)

a worse-smelling flower, the worst-smelling flower
That flower is worse smelling (CMS) That flower is worse-smelling. (AP)
That flower is the worst smelling (noun)

little-known facts
The facts were little known. (CMS) The facts were little-known. (AP)

a much-publicized book
The book, though much publicized, did not sell.
The book was much publicized. (CMS) The book was much-publicized. (AP)

a part-time job
He worked part time. (adverb)
The job was part time for now. (CMS) The job was part-time for now. (AP)

a glassy-eyed stare.
He was glassy eyed. (CMS) He was glassy-eyed. (AP)

low-hanging branches
The branches, low hanging and unkempt, were in my way.
The branches are low hanging. (CMS) The branches are low-hanging. (AP)

high-quality shoes
The shoes were of a high quality. (noun)
The shoes, high quality and expensive, fell apart quickly.
The shoes were high quality. (CMS) The shoes were high-quality. (AP)

pet-friendly park
The park, clean and pet friendly, added quality to the neighborhood.
The park was pet friendly. (CMS) The park was pet-friendly. (AP)

tree-climbing gear
Tree climbing is my hobby. I went tree climbing. (noun)

burned-out workers
The workers, angry and burned out, were unproductive.
The workers were burned out. (CMS) The workers were burned-out. (AP)

over-the-counter medicine
bought the medicine over the counter, it was available over the counter

out-of-style dresses
the dresses are going out of style.
The dresses will be out of style. (CMS) The dresses will be out-of-style. (AP)

game-playing friends
board-game-playing friends
It was a long night of game playing. (noun)

cooking-utensil drawer
The drawer is for cooking utensils. (noun)

7. With some terms, there is some gray area, especially when the two-word term is commonly used and usually a noun, such as high school. Does a hyphen aid readability? If yes, use a hyphen. If not, you may decide to keep it two words. Editors may debate some of these examples and approach them differently. Chicago says it is “never incorrect” to hyphenate them, though. (7.81)

high school sports; high school teacher (no chance of misreading)

open enrollment period (no chance of misreading)

open house night (no chance of misreading)

barbed wire fence (no chance of misreading)

a first-name basis (more clear with a hyphen)

first-person narrative (more clear with a hyphen, and Chicago almost always hyphenates it too.)

small-business owner (without the hyphen, could be read as “business owner who is small.”)

blue-ribbon winner (without the hyphen, could be read as “ribbon winner who is blue.” Also, it’s listed in MW11 and WNW, so there’s no debate.)

multiple-choice test (The word multiple-choice, adj., is listed in MW11 and WNW, so there’s no debate.)

chemistry class skills (This example would likely be treated differently by different editors. I would vote for no hyphen, as I don’t see a possibility of misreading, but you could perhaps convince me otherwise.)

8. Usually, if the dictionary lists a hyphenated adjective, its noun form (-ness, -er) will also be hyphenated.

open-ended (adj.); open-endedness (n.)
first-string (adj.); first-stringer (n.)

For the following tables,

vt.= transitive verb (requires a direct object)
vi.=intransitive verb (does not require a direct object)
v.=can be transitive or intransitive: I will walk. I will walk the dog. I read. I read a book.

after

Usually afterword

AP: No hyphen to form a noun, but use a hyphen to form an adjective or adverb. CMS would agree.

black=dictionaries agree. blue, pink: dictionaries disagree. gray=not listed here, but agrees by default rule. lt. blue, lt. pink: not listed here, but disagrees by default rule.

All words listed in dictionary:

MW11 (CMS’s dictionary)	WNW (AP’s dictionary)
Usually afterword as a noun, but after-word as an adjective If not in MW11 dictionary, hyphenate if used as adjective before noun, but two words elsewhere. He had a snack after school, but after-school snack.	Usually afterword as a noun, but after-word as an adjective If not in dictionary, afterword to form a noun, but after-word to form an adjective, and two words otherwise. the afterlife, but an after-life plan, what happens after life?
1 word / 2 words / Hyphenated / Dictionaries agree / Disagrees w WNW /	1 word / 2 words / Hyphenated / Dictionaries agree / Disagrees w MW11 /
afterbirth	afterbirth
afterburner	afterburner
aftercare	aftercare
afterclap	afterclap
–	afterdamp
afterdeck	afterdeck
aftereffect	aftereffect
afterglow	afterglow
afterguard	–
after-hours	after-hours
afterimage	afterimage
afterlife	afterlife
aftermarket	aftermarket
aftermath	aftermath
aftermost	aftermost
afternoon	afternoon
–	afterpains
after-party	after-party (not in WNW but AP lists it.)
afterpiece	afterpiece
aftershave	after-shave
aftershock	aftershock
aftertaste	aftertaste
after-tax	after-tax
afterthought	afterthought
aftertime	aftertime
afterward	afterward
afterword	afterword
–	afterworld

away

verbs: two words.

The bird will fly away. Please get away from me. Don’t give away that book.

adjectives and nouns: if they are in the dictionary, they are one word.

I have flyaway hair. I need a weekend getaway. The book was a free giveaway for customers.

Most of the two-word verbs are not listed in the dictionary. If not listed in the dictionary, they either appear here in gray or are not included on this list.

MW11 (CMS’s dictionary)		WNW (AP’s dictionary)
back away	vi.	back away	vi.
blow away	vt.	blow away	vt.
break away	vi.	break away	vi.
breakaway	n., adj.	breakaway	n., adj.
caraway	n.	caraway	n.
carry away	vt.	carry away	vt.
castaway	n., adj.	castaway	n., adj.
cutaway	n., adj.	cutaway	n., adj.
fadeaway (sports)	n.	fadeaway (sports)	n.
fall away	vi.	fall away	vi.
fallaway	n., adj.	fallaway	n., adj.
faraway (a faraway place)	adj.	faraway (a faraway place)	adj.
far away (traveling far away, he is far away)	adv.	far away (traveling far away, he is far away)	adv.
flyaway	adj.	flyaway	adj.
foldaway	adj.	foldaway	adj.
getaway	n.	getaway	n.
give away	vt.	give away	vt.
giveaway	n.	giveaway	n.
hideaway	n.	hideaway	n.
lay away	vt.	lay away	vt.
layaway	n.	layaway	n.
pull away	vi.	pull away	vi.
rockaway	n.	rockaway	n.
–		rollaway	adj.
run away	vi.	run away	vi.
runaway	n., adj.	runaway	n., adj.
sleepaway	adj.	–
stow away	vi.	stow away	vi.
stowaway	n.	stowaway	n.
straightaway	adv., adj., n.	straightaway	adv., adj., n.
takeaway (key message, sports term)	n., adj.	–
takeaway (British term for takeout food)	n., adj.	take-away or takeaway (British term for takeout food)	n., adj.
tear away	vt.	tear away	vt.
–		tearaway	adj.
tearaway (British)	n.	tearaway (British)	n.
thataway	adv.	thataway	adv., n.
throw away	vt.	throw away	vt.
throwaway	n., adj.	throwaway	n., adj.
turn away	vt., vi.	turn away	vt., vi.
walk away	vi.	walk away	vi.
walkaway	n.	walkaway	n.

book-

MW11 (CMS’s dictionary)	WNW (AP’s dictionary)
bookbindery	bookbindery
bookbinding	bookbinding
bookcase	bookcase
book club	book club
bookend	bookend
bookkeeping	bookkeeping
–	book learning
book lice	book lice
book lungs	book lungs
bookmaker	bookmaker
bookman	bookman
bookmark	bookmark
book-match (matching grains to achieve a mirror image)	–
–	book matches (matches in a cardboard folder)
bookmobile	bookmobile
bookplate	bookplate
–	bookrack
–	bookrest
–	book review
–	book scorpion
bookseller	bookseller
bookshelf	bookshelf
bookshop	bookshop
bookstall	bookstall
–	bookstand
bookstore	bookstore
–	book tour
book value	book value
bookworm	bookworm

-book

If not in dictionary, make it two words. But hyphenate if using as an adjective before a noun.

MW11 (CMS’s dictionary)	WNW (AP’s dictionary)
If not in dictionary, make it two words: activity book But hyphenate if using it as an adjective before a noun: activity-book fun.	If not in dictionary, make it two words.
account book	account book
audiobook	audiobook
bankbook	bankbook
black book	black book
blue book	blue book
casebook	casebook
chapbook	chapbook
chapter book	chapter book
checkbook	checkbook
class book	class book
codebook	code book
coffee-table book	coffee-table book
coloring book	coloring book
comic book	comic book
commonplace book	commonplace book
cookbook	cookbook
copybook	copybook
date book	datebook
daybook	daybook
Domesday Book	Domesday Book
dream book	dreambook
e-book	e-book
field book	field book
flip book	flipbook (also flip book)
fly book	fly book
funny book	funny book
good book or Good Book	Good Book
grade book	grade book
guest book	guest book
guidebook	guidebook
handbook	handbook
hymnbook	hymnbook
law book	lawbook
logbook	logbook
matchbook	matchbook
netbook	netbook
nonbook	nonbook
notebook	notebook
overbook	overbook
passbook	passbook
phone book	phone book
picture book (n.)	picture book (n.)
picture-book (adj.)	picture-book (adj.)
playbook	playbook
–	pocket book (a small book)
pocketbook	pocketbook (a billfold or purse)
prayer book	prayer book
record book	record book
rule book	rule book
schoolbook	schoolbook
score book	score book
scrapbook	scrapbook
sketchbook	sketchbook
songbook	songbook
sourcebook	sourcebook
statute book	statute book
storybook	storybook
stylebook	stylebook
talking book	talking book
telephone book	telephone book
textbook	textbook
trade book	trade book
white book	white book
workbook	workbook
yearbook	yearbook

class

MW11 (CMS’s dictionary)		WNW (AP’s dictionary)
class act	n.	–
class action	n.	class action	n.
–		class book	n.
class-conscious	adj.	class-conscious	adj.
class consciousness	n.	class consciousness	n.
class interval	n.	–
classmate	n.	classmate	n.
classroom	n.	classroom	n.
–		class struggle	n.
airman first class	n.	airman first class	n.
cabin class	n.	cabin class	n.
–		chattering classes	n.
–		distribution class	n.
first class (sit in first class) (and second class, etc.)	n.	first class (sit in first class) (and second class, etc.)	n.
first-class (first-class treatment, traveling first-class) (and second-class, etc.)	adj., adv.	first-class (first-class treatment, traveling first-class) (and second-class, etc.)	adj., adv.
form class	n.	form class	n.
high-class	adj.	high-class	adj.
–		low-class (informal)	adj.
lower class (the lower class)	n.	lower class (the lower class)	n.
lower-class (lower-class neighborhoods)	adj.	lower-class (lower-class neighborhoods)	adj.
–		lowerclassman	n.
master class	n.	master class	n.
middle class (the middle class)	n.	middle class	n.
middle-class (middle-class families)		middle-class	adj.
middle-classness	n.	–
private first class	n.	private first class	n.
sergeant first class	n.	sergeant first class	n.
tourist class	n.	tourist class	n.
underclassman	n.	underclassman	n.
upper class (the upper class)	n.	upper class (the upper class)	n.
upper-class (upper-class citizens)	adj.	upper-class (upper-class citizens)	adj.
upperclassman	n.	upperclassman	n.
working class (the working class)		working class (the working class)	n.
working-class (working-class citizens)		working-class (working-class citizens)	adj.
world-class	adj.	world-class	adj.

cross

MW11 (CMS’s dictionary)	WNW (AP’s dictionary)
cross action	–
crossbanding	–
crossbar	crossbar
crossbeam	crossbeam
crossbearer	–
–	crossbedded
crossbill	crossbill
crossbones	crossbones
crossbow	crossbow
crossbreed	crossbreed
cross-check	cross-check
cross-claim	–
cross-country	cross-country
crosscourt	crosscourt
–	cross cousin
cross-cultural	cross-cultural
crosscurrent	crosscurrent
crosscut	crosscut
cross-dressing	cross-dressing
cross-examination	cross-examination
cross-eyed	cross-eyed
–	cross-fade
cross-fertile	cross-fertile
cross-fertilize	cross-fertilize
cross-file	cross-file
cross fire	crossfire
cross-grained	cross-grained
crosshair	crosshair
crosshatch	crosshatch
cross-hatching	not listed, so crosshatching, based on crosshatch
crosshead	crosshead
cross-index	cross-index
crossing guard	crossing guard
crossing-over (scientific)	crossing-over (scientific)
cross-legged	cross-legged
crosslet	crosslet
crosslinguistic	–
cross-link	cross-link
cross multiply	–
cross-national	–
crossover (n.) but cross over (v.) a crossover vehicle, plan a crossover, BUT to cross over to the country music genre	crossover (n.) but cross over (v.) a crossover vehicle, plan a crossover, BUT to cross over to the country music genre
cross-ownership	cross-ownership
crosspatch	crosspatch
crosspiece	crosspiece
cross-pollinate	cross-pollinate
cross product	–
cross-purpose	cross-purpose
cross-question	cross-question
cross-react	–
cross-refer	cross-refer
cross-reference	cross-reference
–	cross relation
cross-resistance	–
–	cross-rhythm
crossroad	crossroad
crossruff	crossruff
cross section (n.), but cross-section (v.), cross-sectional (adj.)	cross section (n.), but cross-section (v.), cross-sectional (adj.)
cross-staff	–
cross-stitch	cross-stitch
cross talk	cross-talk
cross-tolerance	–
crosstown	crosstown
cross-trade	–
cross-train	cross-train
crosstrees	crosstrees
cross vault	–
crosswalk	crosswalk
crossway	crossway
crosswind	crosswind
crosswise	crosswise
crossword	crossword
double cross (noun form and genetics)	double cross (noun form and genetics)
double-cross (v. – to betray)	double-cross (v. – to betray)

cyber

orange=additional terms listed in AP Stylebook 2017.

MW11 (CMS’s dictionary)	WNW (AP’s dictionary)
one word / – indicates not listed	one word / two words / not listed in WNW but AP lists it / – indicates not listed
–	cyberattack
cyberbully	cyberbully
cybercafe	cybercafe
cybercitizen	–
–	cyberespionage
–	cyber insurance
–	Cyber Monday
cybernate	cybernate
cybernation	cybernation
cybernaut	cybernaut
cybernetics	cybernetics
cyberporn	–
cyberpunk	cyberpunk
cybersecurity	–
cybersex	cybersex
–	cyber shopping
cyberspace	cyberspace
cyberspeak	–
cybersurfer	–
cyberterrorism	–
–	cyberwar

double

MW11 (CMS’s dictionary)		WNW (AP’s dictionary)
double-A battery (= AA battery)	n.	–
double agent	n.	double agent	n.
double bar	n.	double bar	n.
double-barrel	n.	–
double-barreled	adj.	double-barreled	adj.
double bass	n.	double bass	n.
double bassist	n.	double bassist	n.
double bassoon	n.	double bassoon	n.
double bill	n.	–
double bind	n.	double bind	n.
–		double Blackwall hitch (knot)	n.
double-blind	adj.	double-blind	adj.
double bogey	n.	double bogey	n.
double-bogey	vt.	–
double boiler	n.	double boiler	n.
double bond	n.	double bond	n.
double-breasted	adj.	double-breasted	adj.
double check (a double check)	n.	double-check (a double-check)	n.
double-check (to double-check)	v.	double-check (to double-check)	v.
–		double chin	n.
double-clutch	vi.	–
–		double counterpoint	n.
double-crop	v.	–
double cross (a double cross)	n.	double cross (a double cross)	n.
double-cross (to double-cross)	vt.	double-cross (to double-cross)	vt.
double-crosser	n.	double-crosser	n.
double dagger	n.	double dagger	n.
double date (a double date)	n.	double date (a double date)	n.
double-date (to double-date)	v.	double-date (to double-date)	v.
double-dealing	n., adj.	double-dealing	n.
double-dealer	n.	double-dealer	n.
double-deck (or double-decked)	adj	–
double-decker	n.	double-decker	n.
–		double decomposition	n.
double-digit		double-digit	adj.
double-dipper	n.	double dipper	n.
double-dipping	n.	double dipping	n.
double-dome	n.	–
double door	n.	–
double-double	n.	–
double down	vi.	–
double dribble	n.	double dribble	n.
double Dutch	n.	double Dutch (also double dutch or Double Dutch)	n.
double eagle	n.	double eagle	n.
double-eagle	vt.	–
double-edged	adj.	double-edged	adj.
double-edged sword	n.	double-edged sword	n.
double-ended	adj.	–
double-ender	n.	–
double entendre	n.	double-entendre	n.
double entry		double entry	n.
–		double-entry	adj.
–		double exposure	n.
double-faced (or less commonly double-face)	adj.	double-faced	adj.
double fault	n.	double fault	n.
double-fault	vi.	double-fault	vi.
double feature	n.	double feature	n.
double fertilization	n.	–
–		double flat	n.
double genitive	n.	–
double glazing	n.	double-glazing	n.
Double Gloucester (cheese)	n.	–
doublehanded	adj.	–
doubleheader	n.	double-header	n.
double-helical	adj.	–
double helix	n.	double helix	n.
double-hung	adj.	double-hung	adj., n.
double hyphen	n.	–
double indemnity	n.	double indemnity	n.
double jeopardy	n.	double jeopardy	n.
double-jointed	adj.	double-jointed	adj.
double knit	n.	double-knit	adj.
–		double-minded	adj.
–		double mordent	n.
double negative		double negative	n.
double-park	v.	double-park	v.
double play	n.	double play	n.
double pneumonia	n.	double pneumonia	n.
double prime	n.	–
double-quick	n., adj., adv.	double-quick	n., adj., adv., v.
double reed	n.	double-reed	n., adj.
double refraction	n.	double refraction	n.
double-ring	adj.	–
double salt	n.	double salt	n.
–		double sharp	n.
double-space	v.	double-space	v.
double-spaced	adj., adv.	double-spaced	adj., adv.
double-spacing	n.	double-spacing	n.
doublespeak	n.	doublespeak	n.
doublespeaker	n.	–
double standard		double standard	n.
double star		double star	n.
double-stop	v., n.	double-stop	v., n.
double sugar	n.	–
–		double tackle	n.
double take	n.	double take	n.
double-talk	n., vi.	double talk	n.
double-talker	n.	–
double-team	vt., n.	double-team	vt.
Double Ten	n.	–
doublethink	n.	double-think or doublethink	n.
double time	n.	double time	n.
double-time	vi.	–
double-tongue	vi.	double-tongue	vi.
–		doubletree	n.
double up	vi.	–
double vision	n.	double vision	n.
double whammy	n.	–
double-wide	n.	double-wide (sometimes written doublewide)	n.
daily double	n.	daily double	n.

ever

CMS: Hyphenate before a noun, but make two words after a noun.

an ever-reliable friend
My friend is ever reliable.

AP does not offer specific rules on this topic, but a look at their Ask the Editor shows they generally agree with CMS.

Some permanent constructions are one word (a.k.a. closed compounds). Here are all the closed ever- compounds listed in each dictionary:

MW11 (CMS’s dictionary)		WNW (AP’s dictionary)
everblooming	adj.	–
everduring	adj.	–
everglade(s)	n.	everglade(s)	n.
Everglades (geographical name)	n.	Everglades (geographical name)	n.
evergreen	adj., n.	evergreen	adj., n.
everlasting	adj., n.	everlasting	adj., n.
everlastingly	adv.	everlastingly	adv.
everlastingness	n.	everlastingness	n.
evermore	adv.	evermore	adv.

first

Usually nouns are two words (sometimes one), but adjectives before a noun are hyphenated.

If it’s not listed, it doesn’t mean it’s not acceptable, it just means the dictionary doesn’t feel the need to list it as its own entry, e.g. first edition, first finger.

MW11 (CMS’s dictionary)		WNW (AP’s dictionary)

first aid	n.	first aid	n.
first base	n.	first base	n.
first baseman	n.	first baseman	n.
firstborn	n., adj.	firstborn	n., adj.
first cause	n.	first cause	n.
first class (sitting in first class)	n.	first class (sitting in first class)	n.
first-class (first-class accommodations, to travel first-class)	adj., adv.	first-class (first-class accommodations, to travel first-class)	adj., adv.
first cousin	n.	first cousin	n.
first-degree burn	compound adj. + n.	first-degree burn	compound adj. + n.
first down	n.	first down	n.
first edition	n.	–
first estate	n.	first estate	n.
–		first family	n.
–		first finger	n.
first floor	n.	first floor	n.
firstfruits	n.	first fruits	n.
–		first-generation	adj.
firsthand	adj., adv.	firsthand	adj., adv.
first lady (often First Lady)	n.	first lady (often First Lady)	n.
first lieutenant	n.	first lieutenant	n.
–		first light	n.
first-line	adj.	–
firstling	n.	firstling	n.
firstly	adv.	firstly	adv.
–		first mate	n.
first mortgage	n.	first mortgage	n.
first name	n.	first name	n.
first night *	n.	first night *	n.
first-nighter *	n.	first-nighter *	n.
first off	adv.	–	–
first offender	n.	first offender	n.
first papers	n.	–	n.
first person	n.	first person	n.
–		first quarter	n.
first-rate	adj., adv.	first-rate	adj., adv.
first-rateness	n.	–
first-rater	n.	–
first reading	n.	–
first responder	n.	first responder	n.
first-run	adj.	first-run	adj.
first sergeant	n.	first sergeant	n.
first strike	n.	first strike	n.
first-strike	adj.	first-strike	adj.
first-string	adj.	first-string	adj.
first-stringer	n.	–
first water	n.	first water	n.
first world (often First World)	n.	First World (occasionally first world)	n.

*Note, first night but first-nighter.

half-

CMS: Check MW11. If not listed there, leave nouns as two words, but hyphenate adjectives both before and after the noun. I am half-awake. AND The half-awake residents took shelter. BUT I wore a half shirt. I’m only a half success.

AP: hyphenate if not listed in WNW. (Except terms that should be two words.)

MW11 (CMS’s dictionary)	WNW (AP’s dictionary)
Can be halfword, half-word, or half word, depending.	Can be halfword, half-word, or half word, depending.
1 word / 2 words / Hyphenated / Dictionaries agree / Disagrees w WNW / – indicates not listed	1 word / 2 words / Hyphenated / Dictionaries agree / Disagrees w MW11 / – indicates not listed.
half-and-half	half-and-half
half-assed	half-assed
halfback	halfback
half-baked	half-baked
half bath	–
halfbeak	halfbeak
half binding	half binding
half blood (n.) or half-blood (adj.)	half blood or half-blood (n.); half-blood (adj.). AP prefers half-blood only.
half boot	half boot
half-bound	–
half-bred	–
half-breed	half-breed
half brother	half brother
half-caste	half-caste
–	half-cell
half cock	half cock
half-cocked	half-cocked
half crown	half crown
–	Not listed in WNW, but AP prefers half day (n.), half-day (adj.)
half dime	–
half-dollar	half dollar
half duplex	–
half eagle	half eagle
half-glasses	–
–	half-evergreen
–	half gainer
half-hard	–
halfhearted	halfhearted
half hitch	half hitch
half hour	half-hour
half-hourly	–
half-knot	–
half-length	half-length
half-life	half-life
half-light	half-light
half line	–
half-mast	half-mast *
half-moon	half-moon
–	half mourning
half nelson	half nelson
half note	half note
halfpence	–
halfpenny	halfpenny
half-pint	half pint
half-pipe	–
half plane	–
half rest	–
–	half rhyme
half shell	half shell
half sister	half sister
–	half size
half-slip	half slip
half sole (n.) but half-sole (v.)	half sole (n.) but half-sole (v.)
half sovereign	half sovereign
half-space	–
half-staff	half-staff *
half step	half step
half-timbered	half-timbered
halftime (sports intermission)	halftime (sports intermission)
half-time (half the typical hours)	–
half title	half title
halftone	halftone
half-track	halftrack
half-truth	half-truth
half volley (n.) but half-volley (v.)	half volley (n.) but half-volley (v.)
halfway	halfway
halfway house	halfway house
half-wit	half-wit
half-world	–
time and a half	time and a half

*AP note: Flags are flown at half-mast on ships and at naval stations. Anywhere else on land, they are flown at half-staff.

high

MW11 (CMS’s dictionary)		WNW (AP’s dictionary)
high altar	n.	–
high analysis	adj.	–
high and dry	adj.	–
high and low	adv.	–
high-and-mighty	adj.	–
highball	n., vi.	highball	n., vi.
high beam	n.	high beam	n.
highbinder	n.	highbinder	n.
high blood pressure	n.	high blood pressure	n.
highborn	adj.	highborn	adj.
highboy	n.	highboy	n.
highbred	adj.	highbred	adj.
highbrow	n., adj.	highbrow	n., adj.
highbrowed	adj.	–
highbrowism	n.	–
highbush (plant)	adj.	high-bush (plant)	adj.
high chair	n.	highchair	n.
–		High Church	n.
High Church	adj.	High-Church	adj.
High Churchman	n.	High-Churchman	n.
high-class	adj.	high-class	adj.
high comedy	n.	high comedy	n.
high command	n.	–
high commissioner	n.	high commissioner	n.
–		high-compression	adj.
high-concept	adj.	high-concept	adj.
high-count	adj.	–
high court	n.	–
–		high day	n.
high-def (or less commonly hi-def)	adj., n.	high-def (informal)	adj., n.
high-definition	adj.	high-definition	adj., n.
high-density lipoprotein	n.	high-density lipoprotein	n.
high-end	adj.	high-end	adj.
high-energy	adj.	high-energy	adj.
higher critic	n.	–
higher criticism	n.	higher criticism	n.
higher education	n.	higher education	n.
higher law	n.	–
higher learning	n.	–
higher-up	n.	higher-up	n.
high explosive	n.	high explosive	n.
highfalutin	adj.	highfalutin (also sp. highfaluting)	adj.
high fashion	n.	–
high fidelity	n.	high fidelity	n.
high-fidelity	adj.	–
high five	n.	high-five	n.
high-five	v.	high-five	v.
highflier (or highflyer)	n.	highflier (also sp. highflyer)
high-flown	adj.	high-flown	adj.
high-flying	adj.	highflying	adj.
high frequency	n.	high frequency	n.
high gear	n.	–
High German	n.	High German	n.
high-grade	adj.	high-grade	adj.
high ground	n.	high ground	n.
high-handed	adj.	highhanded	adj.
high-handedly	adv.	highhandedly	adv.
high-handedness	n.	highhandedness	n.
high hat (or hi-hat)	n.	high-hat	n.
high-hat	adj., vt.	high-hat	adj., vt.
high heels	n.	–
High Holidays	n.	High Holidays (also High Holy Days)	n.
high horse	n.
–		high-impact	adj.
hijack (or less commonly highjack)	vt., n.	hijack (or alt. sp. highjack)	vt.
high jinks (or less commonly hijinks)	n.	high jinks (or alt. sp. hijinks or hi-jinks)	n.
high jump	n.	high jump	n.
high-jump	vt.	–
high jumper	n.	–
highland, highlands	n., adj.	highland, highlands	n., adj.
Highlands (geographical name)	n.	Highlands (geographical name)	n.
highlander	n.	highlander	n.
Highland fling	n.	Highland fling	n.
high-level	adj.	high-level	adj.
highlife	n.	high life (also written highlife)	n.
highlight	n., vt.	highlight	n., vt.
highlighter	n.	highlighter	n.
–		high liver	n.
high-low-jack	n.
high mass (often written High Mass)	n.	High Mass	n.
high-minded	adj.	high-minded	adj.
high-mindedly	adv.	high-mindedly	adv.
high-mindedness	n.	high-mindedness	n.
high-muck-a-muck (or high-muckety-muck)	n.	high muck-a-muck (or high muckety-muck)	n.
highness	n.	highness	n.
high noon	n.	high noon	n.
high-octane	adj.	high-octane	adj.
high-pitched	adj.	high-pitched	adj.
high place	n.	high place	n.
High Plains (geographical name)	n.	–
high polymer	n.	–
high-powered (or less commonly high-power)	adj.	high-powered	adj.
high-pressure	adj., vt.	high-pressure	adj., vt.
–		high-priced	adj.
high priest / high priestess	n.	high priest / high priestess	n.
high priesthood	n.	high priesthood	n.
		high-profile	adj.
high relief	n.	high relief	n.
high-rise	n., adj.	high-rise	n., adj.
high road	n.	high road (also written highroad)	n.
high roller	n.	high roller	n.
high-rolling	adj.	high-rolling	adj.
high school	n.	high school	n.
–		high-school	adj.
high schooler	n.	high schooler or high-schooler	n.
high seas	n.	high seas	n.
High Sierra (geographical name)	n.	–
high sign	n.	high sign	n.
–		high society	n.
high-sounding	adj.	high-sounding	adj.
high-speed	adj.	–
high-spirited	adj.	high-spirited	adj.
high-spiritedly	adv.	–
high-spiritedness	n.	–
highspot	n.	–
		high-stepping	adj.
high-sticking	n.	high-sticking (also written high sticking)	n.
high street	n.	–
high-strung	adj.	high-strung	adj.
high style	n.	–
–		high-style	adj.
high table	n.	high table	n.
hightail	vi.	high-tail or hightail	vi.
high tea	n.	high tea	n.
high tech	n.	high tech (also high-tech)	n., adj.
high-tech (or less commonly hi-tech)	adj.	high-tech	adj.
high technology	n.	high technology	n.
high-tension	adj.	high-tension	adj.
high-test	adj.	high-test	adj.
high-ticket	adj.
high tide	n.	high tide	n.
–		high time	n.
high-toned	adj.	high-toned	adj.
high-top	adj.	high-top (also written hightop)	adj.
high-tops	n.	high-tops	n.
high treason	n.	high treason	n.
high-voltage	adj.
high water	n.	high water	n.
high-water	adj.	high-water	adj.
high-water mark	n.	high-water mark	n.
highway	n.	highway	n.
highwayman	n.	highwayman	n.
–		highway patrol	n.
highway robbery	n.	highway robbery	n.
–		high wire	n.
high-wire	adj.	–
high-wrought	adj.	–
–		ace-high	adj.
junior high school	n.	junior high school	n.
senior high school	n.	senior high school	n.
–		waist-high	adj.

home

MW11 (CMS’s dictionary)		WNW (AP’s dictionary)
at home (an at home)	n.	at-home (an at-home)	n.
at-home (at-home recreation)	adj.	–
close to home		–
down-home	adj.	down-home	adj.
funeral home	n.	funeral home	n.
group home	n.	group home	n.
in-home	adj.	–
mobile home	n.	mobile home	n.
motor home	n.	motor home	n.
nonhome	adj.	–
nursing home	n.	nursing home	n.
stay-at-home	adj., n.	–
take-home pay	n.	take-home pay	n.
townhome (but town house)	n.	–

-house

word house or wordhouse. Check dictionary. Exception: in-house (adj.)
Two words if not listed per CMS. (AP does not mention but would surely agree.)

Here are a few examples.

MW11 (CMS’s dictionary)	WNW (AP’s dictionary)
alehouse	alehouse
almshouse	almshouse
art house	art house
backhouse	backhouse
barrelhouse	barrelhouse
bathhouse	bathhouse
bawdy house	bawdyhouse
–	beadhouse
birdhouse	birdhouse
blockhouse	blockhouse
boardinghouse	boardinghouse
boathouse	boathouse
bunkhouse	bunkhouse
–	carriage house
clearinghouse	clearinghouse
clubhouse	clubhouse
coffeehouse	coffeehouse
country house	–
courthouse	courthouse
deckhouse	deckhouse
discount house	discount house
doghouse	doghouse
dollhouse	dollhouse
–	engine house
farmhouse	farmhouse
field house	field house
firehouse	firehouse
flophouse	flophouse
–	freight house
fun house	fun house
gashouse	gashouse
gatehouse	gatehouse
glasshouse	glasshouse
greenhouse	greenhouse
guardhouse	guardhouse
guesthouse	guesthouse
halfway house	halfway house
hash house	hash house
henhouse	henhouse
hothouse	hothouse
icehouse	icehouse
in-house	in-house
jailhouse	jailhouse
lighthouse	lighthouse
lodging house	lodging house
longhouse	longhouse
madhouse	madhouse
manor house	manor house
meetinghouse	meetinghouse
motherhouse	motherhouse
movie house	movie house
nuthouse	nuthouse
open house	open house
opera house	opera house
outhouse	outhouse
packinghouse	packinghouse
penthouse	penthouse
pesthouse	pesthouse
playhouse	playhouse
poorhouse	poorhouse
porterhouse	porterhouse
pothouse	pothouse
powerhouse	powerhouse
public house	public house
roughhouse	roughhouse
row house	row house
safe house	safe house
smokehouse	smokehouse
storehouse	storehouse
roadhouse	roadhouse
rooming house	rooming house
roundhouse	roundhouse
schoolhouse	schoolhouse
slaughterhouse	slaughterhouse
statehouse	statehouse
station house	station house
steak house	steakhouse
summerhouse	summer house
–	taphouse
teahouse	teahouse
tollhouse	tollhouse
townhome	–
town house	town house
tree house	treehouse
warehouse	warehouse
wheelhouse	wheelhouse
whorehouse	whorehouse
workhouse	workhouse

like-

CMS: No thoughts on this topic, but would surely agree would AP’s rule.
The only hyphenated like- word in MW11 is like-minded.

AP: Use a hyphen when like means “similar to.” like-minded, like-natured
But no hyphen for words with their own meanings: likewise, likeness

-like

CMS: One word if listed in MW11. If not listed, hyphenate whether before or after a noun.

businesslike, catlike, childlike, godlike, leaflike, weblike (all in MW11)
BUT statue-like, cell-like (not in MW11)

AP: Do not use a hyphen usually, regardless of dictionary. catlike, statuelike
But use a hyphen to avoid a triple l: cell-like
And use a hyphen with a proper noun: Lyme-like
One exception in AP: flu-like

low

MW11 (CMS’s dictionary)	.	WNW (AP’s dictionary)	.
lowball	vt., n.	lowball	vt., adj.
–		lowballing	n.
low beam	n.	low beam	n.
low blood pressure	n.	low blood pressure	n.
low blow	n.	low blow	n.
lowborn	adj.	lowborn	adj.
lowboy	n.	lowboy	n.
lowbred	adj.	lowbred	adj.
lowbrow	adj., n.	lowbrow	adj., n.
–		low-cal (informal)	adj.
–		Low Church	n.
Low Church	adj.	Low-Church	adj.
Low Churchman	n.	–
–		low-class (informal)	adj.
low comedy	n.	low comedy	n.
–		low-cost	adj.
Low Countries (in Europe, geographical name)	n.	Low Countries (in Europe, geographical name)	n.
low country (often written Low Country)	n.	–
low-country (often written Low-Country)	adj.	–
Low Country (or Lowcountry) (in U.S., geographical name)	n.	–
–		low-cut	adj.
low-density lipoprotein	n.	low-density lipoprotein	n.
low-down	adj.	lowdown	adj.
lowdown	n.	lowdown	n.
low earth orbit	n.	–
low-end	adj.	low-end	adj.
–		lower bound	n.
–		Lower California	n.
Lower Canada	n.	Lower Canada	n.
lowercase * (in lowercase, lowercase letters, please lowercase this.)	n., adj., vt.	lowercase * (in lowercase, lowercase letters, please lowercase this.)	n., adj., vt.
lower class (the lower class)	n.	lower class (the lower class)	n.
lower-class (lower-class homes)	adj.	lower-class (lower-class homes)	adj.
–		lowerclassman	n.
lower criticism	n.	lower criticism	n.
Lower 48 (or lower 48)	n.	lower forty-eight (“usually written lower 48”)	n.
lower fungus	n.	–
–		lower house (often Lower House)	n.
lowermost	adj.	lowermost	adj.
Lower Peninsula (of Michigan)	n.	–
–		lower world	n.
lowest common denominator	n.	lowest common denominator	n.
lowest common multiple	n.	lowest common multiple	n.
lowest terms	n.	–
low frequency	n.	low frequency	n.
Low German	n.	Low German	n.
low-grade	adj.	low-grade	adj.
low-key (or less commonly low-keyed)	adj.	low-key (also low-keyed)	adj.
lowland	n., adj.	lowland	n., adj.
lowlander	n.	lowlander	n.
Lowlands (of Scotland)	n.	Lowlands (of Scotland)	n.
Low Latin	n.	Low Latin	n.
low-level	adj.	low-level	adj.
lowlife	n.	lowlife	n.
low-life	adj.	lowlife	adj.
–		lowlifer	n.
lowlifes (also lowlives)	n.	lowlifes	n.
lowlight	n.	lowlight	n.
low-lying	adj.	low-lying	adj.
low mass (often written Low Mass)	n.	Low Mass	n.
low-minded	adj.	low-minded	adj.
low-mindedly	adv.	low-mindedly	adv.
low-mindedness	n.	low-mindedness	n.
–		low-necked (also low-neck)	adj.
low-pressure	adj.	low-pressure	adj.
–		low-priced	adj.
–		low-profile	adj.
–		low-proof	adj.
low relief	n.	low relief	n.
low-rent	adj.	low-rent	adj.
lowrider	n.	lowrider	n.
low-rise	adj.	low-rise	adj.
low-slung	adj.	–
low-spirited	adj.	low-spirited	adj.
low-spiritedly	adv.	–
low-spiritedness	n.	–
Low Sunday	n.	Low Sunday	n.
low-tech	adj.	low-tech	adj.
–		low-technology	adj.
–		low-tension	adj.
–		low-test	adj.
low tide	n.	low tide	n.
low water	n.	low water	n.
–		low-water mark	n.

*MW11 also has an entry for “lower case,” noun, but does not specify the difference between one word or two. Chicago Manual of Style Online only uses the one-word version, “lowercase,” whether noun or adjective.

middle

MW11 (CMS’s dictionary)		WNW (AP’s dictionary)
middle age	n.	middle age	n.
middle-aged	adj.	middle-aged	adj.
middle-ager	n.	–
Middle Ages	n.	Middle Ages	n.
Middle America	n.	Middle America	n.
middle-American	adj.	Middle American	adj.
Middle American	n.	Middle American	n.
–		Middle Atlantic States	n.
–		middlebreaker	n.
middlebrow	n., adj.	middlebrow	n., adj.
middle C	n.	middle C	n.
middle class (the middle class)	n.	middle class (the middle class)	n.
middle-class (middle-class families)	adj.	middle-class (middle-class families)	adj.
middle-classness	n.	–
middle distance	n.	middle distance	n.
–		middle-distance	adj.
Middle Dutch	n.	–
middle ear	n.	middle ear	n.
Middle East	n.	Middle East	n.
Middle Eastern	adj.	Middle Eastern	adj.
Middle Easterner	n.	Middle Easterner	n.
Middle English	n.	Middle English	n.
middle finger	n.	–
Middle French	n.	Middle French	n.
middle game	n.	–
Middle Greek	n.	Middle Greek	n.
middle ground	n.	middle ground	n.
–		middle guard	n.
Middle High German	n.	Middle High German	n.
Middle Irish	n.	Middle Irish	n.
–		Middle Kingdom	n.
middle lamella	n.	middle lamella	n.
–		Middle Latin	n.
Middle Low German	n.	Middle Low German	n.
middleman	n.	middleman	n.
middle management	n.	middle management	n.
middle manager	n.	middle manager	n.
–		middlemost	adj.
middle name	n.	middle name	n.
middle of the road	n.	–
middle-of-the-road	adj.	middle-of-the-road	adj.
middle-of-the-roader	n.	–
middle-of-the-roadism	n.	–
Middle Passage	n.	middle passage	n.
Middle Persian	n.	–
middle school	n.	middle school	n.
middle schooler	n.	middle schooler (or middle-schooler)	n.
Middle Scots	n.	–
–		middle-sized	adj.
–		Middle States	n.
–		Middle Stone Age	n.
middle term	n.	middle term	n.
middleweight	n.	middleweight	n.
Middle Welsh	n.	–

one

MW11 (CMS’s dictionary)		WNW (AP’s dictionary)
one another	pr.	one another	pr.
one-armed bandit (or less commonly one-arm bandit)	n.	one-armed bandit
one-bagger	n.	one-bagger	n.
–		one-base hit	n.
one-dimensional	adj.	one-dimensional	adj.
one-dimensionality	n.	–
–		one-eighty (also written 180)	n.
onefold	adj.	–
one-handed	adj.	–
one-horned rhinoceros	n.	–
one-horse	adj.	one-horse	adj.
one-liner	n.	one-liner	n.
one-man	adj.	one-man	adj.
one-nighter	n.	one-nighter	n.
one-night stand	n.	one-night stand	n.
one-note	adj.	one-note	adj.
one-off	adj., n.	one-off	adj., n.
one-on-one	adj., adv.	one-on-one	adj., adv., n.
one-piece	adj., n.	one-piece	adj.
one-piecer	n.	–
oneself	pr.	oneself	pr.
one-shot	adj., n.	one-shot	adj.
one-sided	adj.	one-sided	adj.
one-sidedly	adv.	–
one-sidedness	n.	–
one-step	n., vi.	one-step	n., vi.
one-stop	adj.	one-stop	adj.
one-tailed (or less commonly, one-tail)	adj.	–
onetime (former, formerly, one-shot)	adj., adv.	one-time (also onetime) (former, one-shot)	adj.
one-time, one-timed, one-timing, one-timer (n.) (a shot in hockey, soccer, etc.)	vt.	–
one-to-one	adj.	one-to-one	adj.
one-track	adj.	one-track	adj.
one-trick pony	n.	one-trick pony	n.
one-two (boxing)	n.	one-two (boxing)	n.
one-two punch	n.	one-two punch	n.
one up (I’m one up on you.)	adj.	one-up (I’m one-up on you) (also one up)	adj.
one-up, one-upped, one-upping (I will one-up you.)	vt.	one-up, one-upped, one-upping (I will one-up you.)	vt.
one-upmanship (or less commonly one-upsmanship)	n.	one-upmanship	n.
one-way	adj.	one-way	adj.
–		one-woman	adj.
–		Air Force One	n.
anyone (Is anyone there?)	pr.	anyone (Is anyone there?)	pr.
any one (Reading any one of these books will be helpful.)	n.	any one (Reading any one of these books will be helpful.)	n.
A1	adj.	A one (also A 1, A-1)	adj.
day one (often written Day One) (the beginning or first day)	n.	Day One (also day one) (the beginning or first day)	n.
everyone (Everyone is here.)		everyone (Everyone is here.)	pr.
every one (Every one of the students was present.)	n.	every one (Every one of the students was present.)	n.
no one (=nobody) (No one was there.) (Compare to: Not one person was there.)		no one (=nobody) (No one was there.) (Compare to: Not one person was there.)	n.
number one (number one on my list, we’re number one)	n.	number one	n.
number one (the number one salesperson, rule number one)	adj.	–
someone	pr.	someone	n.
square one	n.	square one	n.
twenty-one (blackjack)	n.	twenty-one (blackjack)	n.

open

MW11 (CMS’s dictionary)		WNW (AP’s dictionary)
open admission	n.	open admissions	n.
open adoption	n.	–
open air	n.	open air	n.
open-air	adj.	open-air	adj.
open-and-shut	adj.	open-and-shut	adj.
open arms	n.	–
open bar	n.	open bar	n.
opencast	adj.	–
open chain	n.	open chain	n.
–		open circuit	n.
–		open-circuit	adj.
open city	n.	open city	n.
open dating	n.	–
open door	n.	open door	n.
open-door	adj.	open-door	adj.
open-end	adj.	open-end	adj.
open-ended	adj.	open-ended	adj.
open-endedness	n.	open-endedness	n.
open enrollment	n.	–
open-eyed	adj.	open-eyed	adj.
open-faced (less commonly open-face)	adj.	open-faced (also open-face)	adj.
openhanded (and ly, ness)	adj.	openhanded (and ly, ness)	adj.
open-heart (as in surgery)	adj.	open-heart (as in surgery)	adj.
openhearted (and ly, ness)	adj.	openhearted (and ly, ness)	adj.
open-hearth	adj.	open-hearth	adj.
open house	n.	open house	n.
open-label	adj.	–
open letter	n.	open letter	n.
open loop	n.	–
–		open market	n.
open marriage	n.	–
open mike	n.	–
open-minded (and ly, ness)	adj.	open-minded (and ly, ness)	adj.
openmouthed (and ly, ness)	adj.	open-mouthed	adj.
open-pollinated	adj.	–
–		open-pollination	n.
–		open primary	n.
–		open punctuation	n.
–		open sea	n.
open season	n,.	–
open secret	n.	open secret	n.
open sentence	n.	–
open sesame	n.	open sesame	n.
open shop	n.	open shop	n.
open sight	n.	–
–		open-source	adj.
open stance	n.	–
–		open stock	n.
open syllable	n.	–
open up	v.	–
openwork	n.	openwork	n.
open-worked	adj.	–

quasi

Some words are hyphenated and some aren’t. Here is the full list of quasi- words found in MW11 and WNW.

black=dictionaries agree. gray=not listed but agrees by default. dk. blue/dk. pink: dictionaries disagree. lt. blue/lt. pink: not listed but disagrees by default.

backgrounds: white=one word. blue=two words. yellow=hyphen.

self

self-word

Examples: self-aware, self-conscious, self-control, self-help, self-identity, self-reliant, self-worth
MW11, WNW, CMS, and AP agree.

The only exceptions are not actually compound words: selfhood, selfless, selfness, selfsame, selfward.

One odd term:
MW11 prefers unself-conscious
but CMS disagrees and prefers unselfconscious
WNW prefers unselfconscious

show

For types of television shows, always two words. (game show, reality show, talk show, etc.)

MW11 (CMS’s dictionary)	WNW (AP’s dictionary)
air show	–
art show	–
freak show	freak show
game show	game show
no-show	no-show
peep show	peep show
postshow	–
preshow	–
road show	roadshow
sideshow	sideshow
–	slide show
talent show	talent show
talk show	talk show
trade show	–

style

tapas-style restaurant
we dined tapas-style
the food is tapas style

sentence-style capitalization
use sentence style

forms are usually hyphenated, but noun forms are usually open.

two

MW11 (CMS’s dictionary)	.	WNW (AP’s dictionary)	.
two’s complement	n.	–
two-bagger	n.	two-bagger (slang)	n.
–		two-base hit	n.
two-bit	adj.	two-bit	adj.
two bits	n.	two bits	n.
two-by-four	n., adj.	two-by-four	n., adj.
two cents	n.	two cents	n.
two cents’ worth	n.	two cents’ worth	n.
two-cycle	adj.	two-cycle
two-dimensional	adj.	two-dimensional	adj.
two-dimensionality	n.	two-dimensionality	n.
–		two-dimensionally	adv.
two-edged	adj.	two-edged	adj.
two-faced	adj.	two-faced	adj.
–		two-facedly	adv.
two-facedness	n.	–
twofer	n.	twofer	n.
two-fisted	adj.	two-fisted	adj.
twofold	adj., adv.	twofold	adj., adv.
two-footed	adj.	–
–		two-four	adj.
two-handed	adj.	two-handed	adj.
–		two-hander	n.
–		two-legged	adj.
two-party	adj.	–
twopence (or tuppence)	n.	twopence	n.
twopenny	adj.	twopenny	adj.
two-phase	adj.	two-phase	adj.
two-piece	adj., n.	two-piece	adj.
two-piecer	n.	–
two-ply	adj.	two-ply	adj.
–		two-pointer	n.
–		two-shot	n.
two-sided	adj.	two-sided	adj.
twosome	n.	twosome	n., adj.
two-step	n., vi.	two-step	n., vi.
–		two-stroke	adj.
two-suiter	n.	two-suiter	n.
two-tailed (or less commonly two-tail)	adj.	–
two-time	vt.	two-time	vt.
two-timer	n.	two-timer	n.
two-tone	adj.	two-tone	adj.
two-toned	adj.	–
two-way	adj.	two-way	adj.
two-way street	n.	two-way street	n.
two-wheeler	n.	two-wheeler	n.
Goody Two-shoes (often Goody Two-Shoes)	n.	goody-two-shoes (also goody two-shoes, Goody Two-shoes, Goody Two-Shoes)	n., adj.
goody-two-shoes	adj.	–
–		number two	n.
one-two	n.	one-two	n.
one-two punch	n.	one-two punch	n.
thirty-twomo	n.	thirty-twomo	n.

upper

MW11 (CMS’s dictionary)		WNW (AP’s dictionary)
–		upper bound	n
Upper Canada	n.	Upper Canada	n.
uppercase (in uppercase, uppercase letters, please uppercase this.*)	adj., n., vt.	uppercase (in uppercase, uppercase letters, please uppercase this.*)	adj., n., vt.
upper class (the upper class)	n.	upper class (the upper class)	n.
upper-class (upper-class homes)	adj.	upper-class (upper-class homes)	adj.
upperclassman	n.	upperclassman	n.
upper crust (the upper crust)	n.	upper crust (the upper crust)	n.
upper-crust (upper-crust parties)	adj.	upper-crust (upper-crust parties)	adj.
uppercut	n.	uppercut	n.
upper hand	n.	upper hand	n.
–		upper house (often Upper House)	n.
uppermost	adj., adv.	uppermost	adj., adv.
upperpart	n.	–
Upper Peninsula (of Michigan)	n.	Upper Peninsula (of Michigan)	n.
upper respiratory	adj.	–
fixer-upper	n.	fixer-upper	n.

*MW11 also has an entry for “upper case,” noun, two words, but does not specify the difference between the one-word or two-word noun. Chicago Manual of Style Online only uses the one-word version, “uppercase,” whether noun or adjective. I did find two examples in their Q&A where they used the two-word noun, but there is no distinguishing factor for those, so they seem to favor the one-word noun.

vice

MW11, CMS, and WNW: vice word, vice-word, or viceword, depending on dictionary.

AP has its own simplified rule: two words always. vice word

Here are all listed vice words, including those mentioned by CMS and AP.

MW11 and CMS If not listed, hyphenate per CMS rule.	WNW (AP’s dictionary)	AP differs from WNW! Two words always for consistency!
vice admiral	vice admiral	vice admiral
vice-chairman (not listed)	vice-chairman	vice chairman
vice-chancellor	vice-chancellor	vice chancellor
vice-consul	vice-consul	vice consul
vicegerent	vicegerent	vice regent
vice president	vice president	vice president
vice presidential duties	–	–
vice-principal because not listed	–	vice principal
viceregal	viceregal	*
vice-regent	viceregent	vice regent
vicereine	vicereine	*
viceroy	viceroy	*
viceroyalty	viceroyalty	*
vice-secretary (not listed)	–	vice secretary
vice squad	vice squad	vice squad
vice versa	vice versa	vice versa

*These aren’t technically compound words, i.e., roy would not stand on its own as a word, and viceroyalty, vicereine, and viceregal are all related to viceroy.

miscellaneous

cold (there are more)

MW11		WNW
cold-blooded		coldblooded
coldhearted		coldhearted
warm-blooded		warmblooded
warmed-over		warmed-over
warm front		warm front
warmhearted		warmhearted
I will warm up. (v.) but Let’s do a warm-up. (n.)		I will warm up. (v.) but Let’s do a warm-up. (n.)
surefire	adj.	surefire (or sure-fire)	adj.

MW11 (CMS’s dictionary)	WNW (AP’s dictionary)
quasi contract	quasi contract
quasi corporation	–
quasicrystal	quasicrystal
quasi-governmental	–
quasi-judicial	quasi-judicial
quasi-legislative	–
quasiparticle	quasiparticle
quasiperiodic	–
quasi-public	–
quasi-stellar	quasi-stellar