A. What are compound nouns?

A compound noun is a fixed expression which is made up of more than one word and functions as a noun. Such expressions are frequently combinations of two nouns, e.g. car park, human being [person], science fiction [fiction based on some kind of scientific fantasy]. A number of compound nouns are related to phrasal verbs and these are dealt with in Unit 76.

B. How are compound nouns written?

If you understand both parts of the compound noun, the meaning will usually be clear. Compound nouns are usually written as two words, e.g. tin opener [an opener for tins], bank account [an account in a bank], pedestrian crossing [a place for people to cross a road], but sometimes they are written with a hyphen instead of a space between the words, e.g. self-control [control over your own emotions and reactions]. Sometimes they may be written as one word, e.g. earring, trademark [the symbol of a product], babysitter [someone who stays with a baby/child while parents are out].

Note that there are no strict rules about which compound words should be written in which way. There is a lot of variation even between dictionaries.

C. Stress in compound nouns

Usually the main stress is on the first part of the compound but sometimes it is on the second part. In the common compound nouns below, the word which contains the main stress is underlined.

alarm clock	contact lens	mineral water	voice mail
blood donor	credit card	package holiday	windscreen
burglar alarm	heart attack	steering wheel	windscreen wiper
bus stop	light bulb	tea bag	youth hostel

D. Grammar of compound nouns

Compound nouns may be countable, uncountable or only used in either the singular or the plural. The examples given in C are all countable compound nouns. Here are some examples of common uncountable compound nouns.

air traffic control	computer technology	food poisoning	junk food
birth control	cotton wool	hay fever [allergy to pollen]	mail order
blood pressure	data processing	income tax	pocket money

Here are some examples of common compound nouns used only in the singular.

arms race [two or more countries competing to have the most powerful military]	generation gap
climate change	sound barrier
death penalty	welfare state

Here are some examples of common compound nouns used only in the plural.

grass roots	kitchen scissors	race relations	sunglasses
headphones	luxury goods	roadworks	traffic lights