flower arrangement vs ornament

flower arrangement and ornament both are nouns.

Word	Noun	Adjective	Verb	Adverb
flower arrangement	Yes	No	No	No
ornament	Yes	No	Yes	No

As nouns, ornament is a hypernym of flower arrangement; that is, ornament is a word with a broader meaning than flower arrangement:

Other hypernyms of flower arrangement include decoration, ornamentation, arrangement.

flower arrangement (noun)	ornament (noun)
a decorative arrangement of flowers	something used to beautify

flower arrangement (verb)	ornament (verb)
	make more attractive by adding ornament, colour, etc.
	be an ornament to