fissure vs vallecula

fissure and vallecula both are nouns.

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

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

fissure: (anatomy) a long narrow slit or groove that divides an organ into lobes
vallecula: (anatomy) any furrow or channel on a bodily structure or part

Other hypernyms of fissure include groove.

fissure (noun)	vallecula (noun)
(anatomy) a long narrow slit or groove that divides an organ into lobes	(anatomy) any furrow or channel on a bodily structure or part
a long narrow cleft
a long narrow depression in a surface

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