ornament vs decorate

ornament is a noun but decorate is not a noun.

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

As verbs, ornament and decorate are synonyms defined as:

ornament and decorate: make more attractive by adding ornament, colour, etc.

Other synonyms of ornament include adorn, beautify, embellish, grace.

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

Other hypernyms of ornament include adorn, beautify, deck, embellish, grace.

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

ornament (verb)	decorate (verb)
make more attractive by adding ornament, colour, etc.	provide with decoration
be an ornament to	make more attractive by adding ornament, colour, etc.
	award a mark of honor, such as a medal, to
	be beautiful to look at