demonstrate vs affirm

demonstrate and affirm both are verbs.

Word	Noun	Adjective	Verb	Adverb
demonstrate	No	No	Yes	No
affirm	No	No	Yes	No

As verbs, affirm is a hypernym of demonstrate; that is, affirm is a word with a broader meaning than demonstrate:

demonstrate: establish the validity of something, as by an example, explanation or experiment
affirm: establish or strengthen as with new evidence or facts

Other hypernyms of demonstrate include confirm, corroborate, substantiate, support, sustain.

demonstrate (verb)	affirm (verb)
establish the validity of something, as by an example, explanation or experiment	establish or strengthen as with new evidence or facts
provide evidence for; stand as proof of; show by one's behavior, attitude, or external attributes	to declare or affirm solemnly and formally as true
give an exhibition of to an interested audience	say yes to
march in protest; take part in a demonstration