A compound noun may be written:
2 as one word
3 as a hyphenated word
4 as two words
Explanation:
A compound noun is a noun consisting of two or more words and that can be written as one word like breakfast, bedroom, cupful and headache, as two or more words such as eye shadow, public speaking, post office and washing machine or with a hyphen like lamp-post, tee-shirt, dry-cleaning and air-conditioning.