vouch vs sustain

vouch and sustain both are verbs.

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

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

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

vouch (verb)	sustain (verb)
give supporting evidence	undergo (as of injuries and illnesses)
summon (a vouchee) into court to warrant or defend a title	establish or strengthen as with new evidence or facts
give personal assurance; guarantee	admit as valid
give surety or assume responsibility	supply with necessities and support
	provide with nourishment
	be the physical support of; carry the weight of
	lengthen or extend in duration or space