expire vs succumb

expire and succumb both are verbs.

Word	Noun	Adjective	Verb	Adverb
expire	No	No	Yes	No
succumb	No	No	Yes	No

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

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

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

expire (verb)	succumb (verb)
expel air	consent reluctantly
pass from physical life and lose all bodily attributes and functions necessary to sustain life	be fatally overwhelmed
lose validity