composition vs write on

composition is a noun but write on is not a noun.

Word	Noun	Adjective	Verb	Adverb
composition	Yes	No	No	No
write on	No	No	Yes	No

composition (noun)	write on (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

composition (verb)	write on (verb)
	write about a particular topic