crack vs fissure

crack and fissure both are nouns.

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

As nouns, crack and fissure are synonyms defined as:

Other synonyms of crack include cleft, crevice, scissure.

As nouns, crack and fissure are synonyms defined as:

Other synonyms of crack include chap, cranny, crevice.

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

Other hyponyms of crack include check, chink.

crack (noun)	fissure (noun)
the act of cracking something	(anatomy) a long narrow slit or groove that divides an organ into lobes
a usually brief attempt	a long narrow cleft
a narrow opening	a long narrow depression in a surface
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

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

crack (verb)	fissure (verb)
break suddenly and abruptly, as under tension	break into fissures or fine cracks
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