cleft vs fissure

cleft and fissure both are nouns.

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

As nouns, cleft and fissure are synonyms defined as:

Other synonyms of cleft include crack, crevice, scissure.

cleft (noun)	fissure (noun)
a long narrow cleft	(anatomy) a long narrow slit or groove that divides an organ into lobes
a split or indentation in something (as the palate or chin)	a long narrow cleft
	a long narrow depression in a surface

cleft (adjective)	fissure (adjective)
having one or more indentations reaching nearly to the midrib
split or divided

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