division vs army unit

division and army unit both are nouns.

Word	Noun	Adjective	Verb	Adverb
division	Yes	No	No	No
army unit	Yes	No	No	No

As nouns, army unit is a hypernym of division; that is, army unit is a word with a broader meaning than division:

division (noun)	army unit (noun)
the act or process of dividing	a military unit that is part of an army
an arithmetic operation that is the inverse of multiplication; the quotient of two numbers is computed
the act of dividing or partitioning; separation by the creation of a boundary that divides or keeps apart
one of the portions into which something is regarded as divided and which together constitute a whole
discord that splits a group
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