A compound noun is a noun that is made with two or more words. A compound noun may be usually [noun + noun] or [adjective + noun] or [verb + noun] etc. Each compound noun acts as a single unit and can be modified by adjectives and other nouns.

Example:
1. noun (bus) + noun (Stop) : Is this the bus stop for the number 12 bus?
2. adjective (full) + noun (moon) : I always feel crazy at full moon.
3. verb(break) + noun(fast) : We always eat breakfast at 8am.
4. verb (check) + preposition (out) :Please remember that check-out is at 12 noon.
5. preposition (under) + noun (world) : Do you think the police accept money from the underworld?
6. noun (truck) + adjective (ful) : We need 10 truckfuls of bricks.