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Hyphens in Compound Nouns
Hyphens in Compound Nouns
A single noun made up of two or more words is called a compound noun (e.g., cooking-oil, pickpocket).The rules on whether to use a hyphen, a space, or nothing between the words in a compound noun are inconsistent. In other words, some exist in all three forms (rare), some exist in two forms (common), and some exist is just one form (most common). For example:
- inkwell
, ink well
, ink-well
- iceaxe
, ice axe
, ice-axe
- busstop
, bus stop
, bus-stop
Overarching Guidance
If you follow the process in this flowchart, your compound noun will be safe.
Use a Hyphen to Speed Up Reading
If the one-word version exists, use it. If you're unsure whether to use the two-word version or the hyphenated version, then opt for the hyphenated version. Joining the words in a compound noun with a hyphen(s) is useful to show that the words are the same grammatical entity. It speeds up reading.Compound nouns with prepositions are nearly always hyphenated because it prevents the prepositions being read as different grammatical entities.
Use Your Spellchecker Carefully
It's a good idea to test for the one-word version with a spellchecker or a dictionary. Note that you can't test the hyphenated version or multiple-word version with a spellchecker because it will test the spelling of each word (even with the hyphenated version). In other words, if you check "pick-pocket" or "pick pocket" (which should be "pickpocket"), your spellchecker will not highlight it as an error.More Specific Guidance on Hyphenating a Compound Noun
Here is some more specific guidance on whether to hyphenate a compound noun. Notice that none of the guidance gives a definitive rule. There are always exceptions.noun
+ noun
Examples: cowboy, toothpaste, rainforest, sunflower, eyeball, bus stop
Guidance: Usually one word but frequently two
noun
+ verb
Examples: haircut, rainfall, snowfall, photo shoot
Guidance: Usually one word but sometimes two
noun
+ preposition
Examples: passer-by, hanger-on
Guidance: Nearly always hyphenated
noun
+ gerund
Examples: ballet dancing, mountain climbing, copy-editing, care-giving, bookkeeping
Guidance: Usually two words but frequently hyphenated or rarely one word
one-syllable noun
+ [do-er]
Examples: bookmaker, stocktaker, caregiver, cabdriver, winemaker, frame-maker,
Guidance: Usually one word but occasionally hyphenated
two-or-more-syllable noun
+ [do-er]
Examples: cabinet-maker, barrel-maker, potato grower, chicken farmer, pheasant plucker
Guidance: Usually hyphenated but frequently two words
noun
+ [non-principal words]
+ noun
Examples: daughter-in-law, jack-of-all-trades, mother-of-pearl, birds-of-prey, son-of-a-gun
Guidance: Usually hyphenated
verb
+ preposition
Examples: make-up, sign-off, take-out, check-in, build-up
Guidance: Nearly always hyphenated
verb-ing (participle)
+ noun
Examples: flying saucer, washing machine, swimming pool, running shoes, cooking-oil
Guidance: Nearly always two words but sometimes hyphenated to eliminate ambiguity
preposition
+ verb
Examples: input, uproar, underpass, output, undercut
Guidance: Nearly always one word
preposition
+ noun
Examples: underworld, underground, outpatient, afterlife, offspring
Guidance: Nearly always one word
adjective
+ noun
Examples: black market, red tape, free will, full moon, blackboard, greenhouse, highway
Guidance: Usually two words but sometimes one
Use a Hyphen to Eliminate Ambiguity
You should use a hyphen to eliminate ambiguity or to prevent a reading stutter. Ambiguity or a reader stutter (when readers check back to ensure they've understood the meaning) can occur when the first word of the pairing is a substance (e.g., "water" or "ink"). For example:- water-bottle
/ water bottle
(When the first word is a substance, a hyphen is useful to show the item is not made of that substance.)
- ice-axe
/ ice axe
(Both are acceptable, but "ice-axe" makes it clear that the axe is not made of ice.)
- paper-clip
/ paper clip
/ paperclip
(All 3 are acceptable. However, be aware that "paper clip" could be taken to mean a clip made of paper not a clip for paper.)
- Please pass me the wire-fastener.
- changing-room
/ changing room
(Both are acceptable, but "changing-room" makes it clear that the room is not changing.)
- laughing-gas
/ laughing gas
(Both are acceptable, but "laughing-gas" makes it clear that the gas is not laughing.)
- cooking-oil
/ cooking oil
(Both are acceptable, but "cooking-oil" makes it clear that the oil is not cooking.)
Compound Nouns as Compound Adjectives
This is a key point. If your multi-word compound noun is being used as an adjective to describe another noun, then hyphenate it (regardless of whether it is usually hyphenated or not). For example:- She likes ballet dancing.
- She is a ballet-dancing instructor.
- Paint the bus stop.
- Paint the bus-stop sign.
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