A compound noun is a noun that is made with two or more words. A compound noun is usually [noun + noun] or [adjective + noun], but there are other combinations (see below). It is important to understand and recognize compound nouns. Each compound noun acts as a single unit and can be modified by adjectives and other nouns.

There are three forms for compound nouns:

  1. open or spaced - space between words (tennis shoe)
  2. hyphenated - hyphen between words (six-pack)
  3. closed or solid - no space or hyphen between words (bedroom)

Here are some examples of compound nouns:

noun+nounbus stopIs this the bus stop for the number 12 bus?
fire-flyIn the tropics you can see fire-flies  at night.
footballShall we play football today?
adjective+nounfull moonI always feel crazy at full moon.
blackboardClean the blackboard please.
softwareI can't install this software  on my PC.
verb(-ing)+nounbreakfastWe always eat breakfast  at 8am.
washing machinePut the clothes in the red washing machine.
swimming poolWhat a beautiful swimming pool!
noun+verb(-ing)sunriseI like to get up at sunrise.
haircutYou need a haircut.
train-spottingHis hobby is train-spotting.
verb+prepositioncheck-outPlease remember that check-out  is at 12 noon.
noun+prepositional phrasemother-in-lawMy mother-in-law  lives with us.
preposition+noununderworldDo you think the police accept money from the underworld?
noun+adjectivetruckfulWe need 10 truckfuls of bricks.

Pronunciation

Compound nouns tend to have more stress on the first word. In the phrase "pink ball", both words are equally stressed (as you know, adjectives and nouns are always stressed). In the compound noun "golf ball", the first word is stressed more (even though both words are nouns, and nouns are always stressed). Since "golf ball" is a compound noun we consider it as a single noun and so it has a single main stress - on the first word. Stress is important in compound nouns. For example, it helps us know if somebody said "a GREEN HOUSE" (a house which is painted green) or "a GREENhouse" (a building made of glass for growing plants inside).

British/American differences

Different varieties of English, and even different writers, may use the open, hyphenated or closed form for the same compound noun. It is partly a matter of style. There are no definite rules. For example we can find:

  • container ship
  • container-ship
  • containership

If you are not sure which form to use, please check in a good dictionary.

Plural Forms of Compound Nouns

In general we make the plural of a compound noun by adding -s to the "base word" (the most "significant" word). Look at these examples:

singularplural
a tennis shoethree  tennis shoes
one assistant headmasterfive  assistant headmasters
the sergeant majorsome  sergeants major
a mother-in-lawtwo mothers-in-law
an assistant secretary of statethree  assistant secretaries of state
my toothbrushour toothbrushes
a woman-doctorfour women-doctors
a doctor of philosophytwo  doctors of philosophy
a passerby, a passer-bytwo passersby , two passers-by

Note that there is some variation with words like spoonful or truckful. The old style was to say spoonsful or trucksful for the plural. Today it is more usual to say spoonfuls or truckfuls. Both the old style (spoonsful) and the new style (spoonfuls) are normally acceptable, but you should be consistent in your choice. Here are some examples:

 old style plural (very formal)new style plural
teaspoonfulteaspoonsful  of sugarteaspoonfuls  of sugar
truckfultrucksful  of sandtruckfuls  of sand
bucketfulbucketsful  of waterbucketfuls  of water
cupfulcupsful  of ricecupfuls  of rice

Some compound nouns have no obvious base word and you may need to consult a dictionary to find the plural:

  • higher-ups
  • also-rans
  • go-betweens
  • has-beens
  • good-for-nothings
  • grown-ups

Note that with compound nouns made of [noun + noun] the first noun is like an adjective and therefore does not usually take an -s. A tree that has apples has many apples, but we say an apple tree, not apples treematchbox not matchesboxtoothbrush not teethbrush.

With compound nouns made of [noun + noun] the second noun takes an -s for plural. The first noun acts like an adjective and as you know, adjectives in English are invariable. Look at these examples:

long plural form becomes →plural compound noun
[noun + noun]
100 trees with apples100  apple trees
1,000 cables for telephones1,000  telephone cables
20 boxes for tools20  tool boxes
10 stops for buses10 bus stops
4,000 wheels for cars4,000  car wheels

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