vouch vs affirm

vouch and affirm both are verbs.

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

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

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

vouch (verb)	affirm (verb)
give supporting evidence	establish or strengthen as with new evidence or facts
summon (a vouchee) into court to warrant or defend a title	to declare or affirm solemnly and formally as true
give personal assurance; guarantee	say yes to
give surety or assume responsibility