trilogy vs triad

trilogy and triad both are nouns.

Word	Noun	Adjective	Verb	Adverb
trilogy	Yes	No	No	No
triad	Yes	No	No	No

As nouns, triad is a hypernym of trilogy; that is, triad is a word with a broader meaning than trilogy:

trilogy: a set of three literary or dramatic works related in subject or theme
triad: a set of three similar things considered as a unit

Other hypernyms of trilogy include trio, triple, triplet.

trilogy (noun)	triad (noun)
a set of three literary or dramatic works related in subject or theme	a three-note major or minor chord; a note and its third and fifth tones
	three people considered as a unit
	a set of three similar things considered as a unit
	the cardinal number that is the sum of one and one and one