foot vs army unit

foot and army unit both are nouns.

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

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

foot (noun)	army unit (noun)
travel by walking	a military unit that is part of an army
any of various organs of locomotion or attachment in invertebrates
the pedal extremity of vertebrates other than human beings
lowest support of a structure
a support resembling a pedal extremity
the part of the leg of a human being below the ankle joint
(prosody) a group of 2 or 3 syllables forming the basic unit of poetic rhythm
an army unit consisting of soldiers who fight on foot
the lower part of anything
a member of a surveillance team who works on foot or rides as a passenger
a linear unit of length equal to 12 inches or a third of a yard