differ vs vary

differ and vary both are verbs.

Word	Noun	Adjective	Verb	Adverb
differ	No	No	Yes	No
vary	No	No	Yes	No

As verbs, vary is a hyponym of differ; that is, vary is a word with a more specific, narrower meaning than differ:

Other hyponyms of differ include depart, deviate, diverge, contrast, counterpoint.

differ (verb)	vary (verb)
be of different opinions	become different in some particular way, without permanently losing one's or its former characteristics or essence
be different	make something more diverse and varied
	be at variance with; be out of line with
	be subject to change in accordance with a variable