Region (mathematical analysis) definition

(1) A part of an animal that has a special function or is supplied by a given artery or nerve

"In the abdominal region"

(2) A knowledge domain that you are interested in or are communicating about

"It was a limited domain of discourse"

"Here we enter the region of opinion"

"The realm of the occult"

(3) The extended spatial location of something

"The farming regions of France"

"Religions in all parts of the world"

"Regions of outer space"

(4) A large indefinite location on the surface of the Earth

"Penguins inhabit the polar regions"

(5) The approximate amount of something (usually used prepositionally as in `in the region of')

"It was going to take in the region of two or three months to finish the job"

"The price is in the neighborhood of $100"