A compound noun is made up of two or more words used as one noun.
Each one of these words has its own distinct meaning.
Compound nouns are classified into three categories according to form: solid, open, and hyphenated.
A combined or solid compound noun is formed by putting two words together to form a single word.
Examples:
A separate or open compound noun is made up of two or three words separately written.
Examples:
A hyphenated compound noun is made up of two or three words joined by hyphen/s.
Examples: