sector vs piece of ground

sector and piece of ground both are nouns.

Word	Noun	Adjective	Verb	Adverb
sector	Yes	No	No	No
piece of ground	Yes	No	No	No

As nouns, piece of ground is a hypernym of sector; that is, piece of ground is a word with a broader meaning than sector:

Other hypernyms of sector include parcel, parcel of land, piece of land, tract.

sector (noun)	piece of ground (noun)
measuring instrument consisting of two graduated arms hinged at one end	an extended area of land
a particular aspect of life or activity
a social group that forms part of the society or the economy
a portion of a military position
the minimum track length that can be assigned to store information; unless otherwise specified a sector of data consists of 512 bytes
a plane figure bounded by two radii and the included arc of a circle