Compound nouns

Words can be combined to form compound nouns. These are very common, and new combinations are invented almost daily. They normally have two parts. The first part tells us what kind of object or person it is, or what its purpose is. The second part identifies the object or person in question. Compound nouns often have a meaning that is different, or more specific, than the two separate words.

First part: type or purpose	Second part: what or who	Compound noun
police	man	policeman
boy	friend	boyfriend
fish	tank	water tank
dining	table	dining-table

You have noticed that the compound noun can be written either as a single word, as a word with a hyphen, or as two words. There are no clear rules about this. A good rule of thumb is to write the most common compound nouns as one word, and the others as two words.

The elements in a compound noun are very diverse parts of speech.

Compound elements	Examples
noun + noun	bedroom water tank motorcycle printer cartridge
noun + verb	rainfall haircut train-spotting
noun + adverb	hanger-on passer-by
verb + noun	washing machine driving licence swimming pool
verb + adverb	lookout take-off drawback
adverb + noun	onlooker bystander
adjective + verb	dry-cleaning public speaking
adjective + noun	greenhouse software redhead
adverb + verb	output overthrow upturn input

Pronunciation

Stress is important in pronunciation, as it distinguishes between a compound noun and an adjective with a noun. In compound nouns, the stress usually falls on the first syllable.