rift vs fissure

rift and fissure both are nouns.

Word	Noun	Adjective	Verb	Adverb
rift	Yes	No	No	No
fissure	Yes	No	Yes	No

As nouns, fissure is a hypernym of rift; that is, fissure is a word with a broader meaning than rift:

Other hypernyms of rift include cleft, crack, crevice, scissure.

rift (noun)	fissure (noun)
a personal or social separation (as between opposing factions)	(anatomy) a long narrow slit or groove that divides an organ into lobes
a narrow fissure in rock	a long narrow cleft
a gap between cloud masses	a long narrow depression in a surface

rift (verb)	fissure (verb)
	break into fissures or fine cracks