demonstrate vs demonstrator

demonstrate is not a noun while demonstrator is a noun.

Word	Noun	Adjective	Verb	Adverb
demonstrate	No	No	Yes	No
demonstrator	Yes	No	No	No

demonstrate (noun)	demonstrator (noun)
	someone who participates in a public display of group feeling
	someone who demonstrates an article to a prospective buyer
	a teacher or teacher's assistant who demonstrates the principles that are being taught

demonstrate (verb)	demonstrator (verb)
establish the validity of something, as by an example, explanation or experiment
provide evidence for; stand as proof of; show by one's behavior, attitude, or external attributes
give an exhibition of to an interested audience
march in protest; take part in a demonstration