domain

a particular environment or walk of life; "his social sphere is limited"; "it was a closed area of employment"; "he's out of my orbit"

territory over which rule or control is exercised; "his domain extended into Europe"; "he made it the law of the land"

(mathematics) the set of values of the independent variable for which a function is defined

people in general; especially a distinctive group of people with some shared interest; "the Western world"

the content of a particular field of knowledge