compoundnoun
A compound noun is a noun formed by combining two or more words to function as a single nominal unit. In English, compounds can designate concrete objects, abstract concepts, or roles, and their meaning may be fully predictable from the parts or idiomatic and specialized.
Orthography and forms vary. Closed forms join the elements into one word (bookcase, toothpaste); open forms separate
Most English compound nouns are noun-noun and typically right-headed: the rightmost noun supplies the main category
Usage and history: Compound nouns are highly productive in English, especially for technology, culture, and everyday