diptych vs art

diptych and art both are nouns.

Word	Noun	Adjective	Verb	Adverb
diptych	Yes	No	No	No
art	Yes	No	No	No

As nouns, art is a hypernym of diptych; that is, art is a word with a broader meaning than diptych:

diptych: a painting or carving (especially an altarpiece) on two panels (usually hinged like a book)
art: the products of human creativity; works of art collectively

Other hypernyms of diptych include fine art.

diptych (noun)	art (noun)
a painting or carving (especially an altarpiece) on two panels (usually hinged like a book)	the creation of beautiful or significant things
	the products of human creativity; works of art collectively
	a superior skill that you can learn by study and practice and observation
	photographs or other visual representations in a printed publication