co-author vs composition

co-author is not a noun while composition is a noun.

Word	Noun	Adjective	Verb	Adverb
co-author	No	No	Yes	No
composition	Yes	No	No	No

co-author (noun)	composition (noun)
	the act of creating written works
	musical creation
	something that is created by arranging several things to form a unified whole
	the way in which someone or something is composed
	the spatial property resulting from the arrangement of parts in relation to each other and to the whole
	an essay (especially one written as an assignment)
	a musical work that has been created
	art and technique of printing with movable type
	a mixture of ingredients

co-author (verb)	composition (verb)
be a co-author on (a book, a paper)