illustrate vs ornament

illustrate is not a noun while ornament is a noun.

Word	Noun	Adjective	Verb	Adverb
illustrate	No	No	Yes	No
ornament	Yes	No	Yes	No

As verbs, ornament is a hypernym of illustrate; that is, ornament is a word with a broader meaning than illustrate:

Other hypernyms of illustrate include adorn, beautify, decorate, embellish, grace.

illustrate (noun)	ornament (noun)
	something used to beautify

illustrate (verb)	ornament (verb)
clarify by giving an example of	make more attractive by adding ornament, colour, etc.
depict with an illustration	be an ornament to
supply with illustrations