I did not understand compound noun.

Hello,

When two or more nouns are combined together to form a single noun, it is known as a compound noun. 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).

They are written in various ways:

1. as one word: policeman, girlfriend, etc.

2. as two words joined by a hyphen: brothers-in-law, father-in-law, dining-table, etc.

3. as two separate words: fish tank, washing machine, living room, table tennis, etc.