Compound Nouns

What Are Compound Nouns? (with Examples)

A compound noun is a noun made from at least two words. There are three forms for compound nouns:

• Compound nouns with spaces
• Compound nouns without spaces
• Compound nouns with hyphens.

Easy Examples of Compound Nouns

• With spaces: swimming pool, grey matter, fish tank
• With no spaces: shotgun, housework, eyelid
• With hyphens: baby-sitter, laughing-gas, daughter-in-law

Real-Life Examples of Compound Nouns

• Whenever the lion fish in the fish tank in the captain's ready room died, it was always a sad moment. (Patrick Stewart, Star Trek's Jean Luke Picard)
• Polygraph tests are 20th-century witchcraft. (US politician Sam Ervin)
• Those you helped will remember you when the forget-me-nots have withered. (Preacher Charles Spurgeon)

Most compound nouns are made from the following components:

• noun + noun: Bath tub, seaman, wall-paper
• adjective + noun: full moon, highway, whiteboard

Other common combinations include:

• verb + noun: washing machine, driving licence, breakfast
• noun + verb: sunrise, rainfall, haircut
• preposition + noun: influx, onlooker, bystander
• preposition + verb: output, input, overthrow
• verb + preposition: checkout, take-off, drawback

Why Compound Nouns Are Important

There are three key issues related to compound nouns.

(Issue 1) Choosing the correct version (i.e., the version with spaces, nothing or hyphens)

Choosing the right or best form of a compound noun can be a nightmare. Here's the situation:

• Some compound nouns were always the one-word version (e.g., keyboard)
• Some two-word ones have transitioned to a one-word version (e.g., snow man to snowman)
• Some two-word ones are transitioning to a one-word version (e.g., eye opener to eyeopener).
• Some two-word ones are not transitioning (e.g., peace pipe)
• Some compound nouns were always the hyphenated version (e.g., self-control).
• Some two-word ones have transitioned to a hyphenated version (e.g., play off to play-off and soon playoff).
• Some two-word ones are transitioning to a hyphenated version (e.g., ice cream to ice-cream).
• Some exist in two versions (e.g., ice-axe or ice axe but not iceaxe)
• Some exist in all three versions (e.g., chatroom, chat-room, chat room )

To give yourself the best chance of hitting the right or best version, go through the following checks:

(Check 1) Check if the one-word version exists using your spellchecker or a dictionary. If it does, then happy days – you're done. If it doesn't, go to Check 2.

(Check 2) Check if the hyphenated version exists using a dictionary. (You can't use your spellchecker because it will treat the hyphen like a space, check the spelling of the sub-words either side, and trust that you know what you're doing with compound nouns. (Yeah, thanks for that, Microsoft.) If it does exist, you're done. If it doesn't, do Check 3, Check 4, and Check 5.

Here's some guidance on the types of compound nouns that should always be hyphenated:

• A noun in the form "role"-"role" (e.g., student-athlete, soldier-poet, boy-child)
• Nouns with a preposition in the middle (e.g., man-of-war, brothers-in-arms)
• Titles of relatives with great (e.g., great-grandmother, great-great-grandson)
• Fractions written in full (e.g., two-thirds, one-quarter)
• Titles with vice and elect (e.g., president-elect, vice-chair)
• Words with "self" (e.g., self-awareness, self-restraint)

Read more about prefixes. (Check 3) You're now left with the two-word version, which you should use unless it makes your sentence ambiguous.

• I like braising steak.
(This could be a comment about how you like to cook steak, so write braising-steak to eliminate the ambiguity.)
• I need a wire fastener.
(This could be construed as fastener made of wire, so write wire-fastener to eliminate the ambiguity.)

(Check 4) If there was no ambiguity, then you're still left with the two-word version, which you should use unless you feel the urge to hyphenate it so your readers can spot it as a single entity in a flash.

• The overwhelming challenge initially is getting to positive cash-flow. (Businessman John Mackey)
• I actually have this fantasy of giving up my cell-phone. (Actress Julia Stiles)
• Domain names and websites are the new real-estate. (Entrepreneur Marc Ostrofsky)

The hyphenated versions stand out as single entities, making them easier to read. That's the justification.

By hyphenating a two-word compound noun, you're contributing to its transition to the hyphenated version and even the one-word version. Be aware that even though your intent might be to make your readers' absorption of your words easier for them, you are running the risk of annoying some of them if you hyphenate a well-established two-worder.

(Check 5) If you've put a hyphen in your compound noun to make it stand out more clearly as a single entity, think about that decision again. Still happy? Then go for it.

Top Tip

Google's Ngram Viewer scans millions of books in a flash. It is simple to use. Use it to help with your decision on whether to use one word, two words, or a hyphenated word for your compound noun.

Here is an example with icecream, ice-cream, and ice cream.

(Issue 2) Forming the plural of a compound noun.

Compound nouns with hyphens (e.g., brother-in-law) and compound nouns with spaces (e.g., Knight Templar) usually form their plurals by pluralizing the principal word.

• I used to have two brothers-in-law. One was a karate expert, who later joined the army. The first time he saluted, he killed himself. (Comedian Henny Youngman)
• The Knights Templar were a sort of medieval SAS. (Historian Dan Jones)

When there is no obvious principal word, add s (or es) to the end of the compound (e.g., forget-me-nots)

• Two lieutenant generals presided over the courts-martial. (There is debate over the principal word in court-martial, but courts-martial is about twice as common as court-martials. Here's evidence.)

(Issue 3) Creating the possessive form of a compound noun like mother-in-law.

With compound noun like mother-in-law, the possessive form is created by adding 's to the end, regardless of whether it is singular or plural.

Singular	Plural
sister-in-law's car	sisters-in-law's husbands
colonel-in-chief's arrival	colonels-in-chief's meeting
maid of honour's bouquet	maids of honour's arrival

Key Points

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