plane section vs expanse

plane section and expanse both are nouns.

Word	Noun	Adjective	Verb	Adverb
plane section	Yes	No	No	No
expanse	Yes	No	No	No

As nouns, expanse is a hypernym of plane section; that is, expanse is a word with a broader meaning than plane section:

plane section: (geometry) the area created by a plane cutting through a solid
expanse: the extent of a 2-dimensional surface enclosed within a boundary

Other hypernyms of plane section include area, surface area.

plane section (noun)	expanse (noun)
(geometry) the area created by a plane cutting through a solid	the extent of a 2-dimensional surface enclosed within a boundary
	a wide scope
	a wide and open space or area as of surface or land or sky