uphold vs sustain

uphold and sustain both are verbs.

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

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

uphold (verb)	sustain (verb)
stand up for; stick up for; of causes, principles, or ideals	undergo (as of injuries and illnesses)
support against an opponent	establish or strengthen as with new evidence or facts
keep or maintain in unaltered condition; cause to remain or last	admit as valid
	supply with necessities and support
	provide with nourishment
	be the physical support of; carry the weight of
	lengthen or extend in duration or space