circulate vs circular

circulate is not a noun while circular is a noun.

Word	Noun	Adjective	Verb	Adverb
circulate	No	No	Yes	No
circular	Yes	Yes	No	No

circulate (noun)	circular (noun)
	an advertisement (usually printed on a page or in a leaflet) intended for wide distribution

circulate (adjective)	circular (adjective)
	having the shape or form of a circle
	describing a circle; moving in a circle

circulate (verb)	circular (verb)
cause to become widely known
become widely known and passed on
move around freely from person to person or from place to place
move through a space, circuit or system, returning to the starting point
cause to be distributed
cause to move in a circuit or system