fissure vs crack

fissure and crack both are nouns.

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

As nouns, fissure and crack are synonyms defined as:

Other synonyms of fissure include cleft, crevice, scissure.

As nouns, fissure and crack are synonyms defined as:

Other synonyms of fissure include chap, cranny, crevice.

As verbs, crack is a hypernym of fissure; that is, crack is a word with a broader meaning than fissure:

fissure (noun)	crack (noun)
(anatomy) a long narrow slit or groove that divides an organ into lobes	the act of cracking something
a long narrow cleft	a usually brief attempt
a long narrow depression in a surface	a narrow opening
	a purified and potent form of cocaine that is smoked rather than snorted; highly addictive
	a blemish resulting from a break without complete separation of the parts
	witty remark
	a sudden sharp noise
	a long narrow cleft
	a long narrow depression in a surface
	a chance to do something

fissure (adjective)	crack (adjective)
	of the highest quality

fissure (verb)	crack (verb)
break into fissures or fine cracks	break suddenly and abruptly, as under tension
	become fractured; break or crack on the surface only
	break partially but keep its integrity
	cause to become cracked
	reduce (petroleum) to a simpler compound by cracking
	break into simpler molecules by means of heat
	pass through (a barrier)
	tell spontaneously
	hit forcefully; deal a hard blow, making a cracking noise
	suffer a nervous breakdown
	make a sharp sound
	make a very sharp explosive sound
	gain unauthorized access computers with malicious intentions