division vs cleavage

division and cleavage both are nouns.

Word	Noun	Adjective	Verb	Adverb
division	Yes	No	No	No
cleavage	Yes	No	No	No

As nouns, cleavage is a hyponym of division; that is, cleavage is a word with a more specific, narrower meaning than division:

division (noun)	cleavage (noun)
the act or process of dividing	the act of cleaving or splitting
an arithmetic operation that is the inverse of multiplication; the quotient of two numbers is computed	the line formed by a groove between two parts (especially the separation between a woman's breasts)
the act of dividing or partitioning; separation by the creation of a boundary that divides or keeps apart	(embryology) the repeated division of a fertilised ovum
one of the portions into which something is regarded as divided and which together constitute a whole	the breaking of a chemical bond in a molecule resulting in smaller molecules
discord that splits a group	the state of being split or cleft
an army unit large enough to sustain combat
a group of ships of similar type
a unit of the United States Air Force usually comprising two or more wings
an administrative unit in government or business
(botany) taxonomic unit of plants corresponding to a phylum
(biology) a group of organisms forming a subdivision of a larger category
a league ranked by quality