Occasionally, we encounter compound nouns: two nouns joined together to create a new meaning. In these cases, the first noun modifies the second, like an adjective, replacing the need for the possessive form (‘s and of). For instance:
Compound nouns with two separate words
- School bus
 - Car park
 - Bus stop
 - Car key
 - Ice cream
 
Compound nouns used as one word
- toothpaste
 - haircut
 - bathroom
 
Compound nouns linked with a hyphen
- letter-box
 - dry-cleaning
 - father-in-law
 
Containers
We often use compound nouns to refer to a container, which is usually empty, such as a tea cup, a wine glass, a beer glass, a matchbox, etc.
Example
- Can you pass me those tea cups?
 - She keeps the insects that she catches in that matchbox.
 
And we use noun + of + noun more often to refer to a container with its content. For example: a cup of tea, a glass of wine, a glass of beer, a box of matches, etc.
Example
- Would you like a cup of tea?
 - Do you have a box of matches? I need to light this candle.
 
References