quarter section vs area unit

quarter section and area unit both are nouns.

Word	Noun	Adjective	Verb	Adverb
quarter section	Yes	No	No	No
area unit	Yes	No	No	No

As nouns, area unit is a hypernym of quarter section; that is, area unit is a word with a broader meaning than quarter section:

quarter section: a land unit equal to a quarter of a section (160 acres) and measuring 1/2 mile on a side
area unit: a system of units used to measure areas

Other hypernyms of quarter section include square measure.

quarter section (noun)	area unit (noun)
a land unit equal to a quarter of a section (160 acres) and measuring 1/2 mile on a side	a system of units used to measure areas