Here are some examples:
* Compound nouns written as one word:
* *schoolhouse*
* *firefighter*
* *rainbow*
* Compound nouns written as two words:
* *post office*
* *high school*
* *dining room*
* Compound nouns written with a hyphen:
* *mother-in-law*
* *check-in*
* *self-service*
There are many different types of compound nouns, and they can be formed by combining different types of words.