interior decoration vs ornament

interior decoration and ornament both are nouns.

Word	Noun	Adjective	Verb	Adverb
interior decoration	Yes	No	No	No
ornament	Yes	No	Yes	No

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

interior decoration: decoration consisting of the layout and furnishings of a livable interior
ornament: something used to beautify

Other hypernyms of interior decoration include decoration, ornamentation.

interior decoration (noun)	ornament (noun)
the trade or act of decorating the interior of a building or room, especially with regard to color combination, paint, fabrics, carpeting, etc.	something used to beautify
decoration consisting of the layout and furnishings of a livable interior

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