Page 389 - Practical English Usage 3ed - Michael Swan, Oxford

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milk chocolate (a kind of chocolate) chocolate milk (a kind of milk)
a horse race (a kind of race)
a race horse (a kind of horse)
a book case (a kind of case)
noun + noun (1): basic information 385
385 noun + noun (1): basic information 1 milk chocolate; chocolate milk
Many common ideas in English are expressed by noun + noun compounds. In this structure. the first noun modifies or describes the second. a little like an adjective. Compare:
mineral water (a kind of water)
Noun + noun expressions can often be changed into structures where the second noun becomes a subject and the first an object.
an oil well (= a well that produces oil)
a sheepdog (= a dog that looks after sheep)
a Birmingham man (= a man who comes from Birmingham) the airport bus (= the bus that goes to the airport)
2 the first noun is singular
Note that the first noun is usually singular in form. even if it has a plural meaning. (For exceptions. see 531.)
a shoe shop (= a shop that sells shoes)
a horse race (= a race for horses) trouser pockets (= pockets in trousers) a toothbrush (= a brush for teeth) a ticket office (= an office that sells tickets)
3 articles
Articles belonging to the first (modifying) noun are dropped in noun + noun combinations.
army officers (= officers in the army)
a sun hat (= a hat that protects you against the sun)
4 more than two nouns
More than two nouns can be put together. A group of two nouns can modify a third noun. these can modify a fourth. and so on.
oil production costs road accident research centre
This kind of structure is very common in newspaper headlines (see 240) because it saves space.
FURNITURE FACTORY PAY CUT ROW
5 other structures
Not all compound ideas can be expressed by a noun + noun structure. Sometimes it is necessary to use a structure with ofor another preposition; sometimes a structure with possessive's is used.
a feeling ofdisappointment (NOT a tiisttf'f'6intf'ltentfeeling)
letters from home (NOT h6me lem:rs) cow's milk (NOT etlW milk)
For more details. see 386.
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