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 second part identifies the object or person in question (man, friend, tank, table, room). The first part tells us what kind of object or person it is, or what its purpose is (police, boy, water, dining, bed):
The two parts may be written in a number of ways :
1. as one word.
Example: policeman, boyfriend
2. as two words joined with a hyphen.
3. as two separate words.
Example: fish tank.
The two parts may be:
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
adjective + noun greenhouse software redhead
adjective + verb dry-cleaning public speaking
adverb + noun onlooker bystander
adverb + verb* output overthrow upturn input
Compound nouns often have a meaning that is different from the two separate words.
Many common compound nouns are formed from phrasal verbs (verb + adverb or adverb + verb).
Examples: breakdown, outbreak, outcome, cutback, drive-in, drop-out, feedback, flyover, hold-up, hangover, outlay, outlet, inlet, makeup, output, set-back, stand-in, takeaway, walkover.