pass away vs succumb

pass away and succumb both are verbs.

Word	Noun	Adjective	Verb	Adverb
pass away	No	No	Yes	No
succumb	No	No	Yes	No

As verbs, succumb is a hyponym of pass away; that is, succumb is a word with a more specific, narrower meaning than pass away:

pass away: pass from physical life and lose all bodily attributes and functions necessary to sustain life
succumb: be fatally overwhelmed

Other hyponyms of pass away include abort, asphyxiate, stifle, suffocate, buy it, pip out, drown, predecease, famish, starve, fall, yield.

pass away (verb)	succumb (verb)
pass from physical life and lose all bodily attributes and functions necessary to sustain life	consent reluctantly
go out of existence	be fatally overwhelmed