domain

(noun) a particular environment or walk of life. Synonyms: sphere, area, orbit, field, arena. Examples: "His social sphere is limited." "It was a closed area of employment." "He's out of my orbit."

(noun) territory over which rule or control is exercised. Synonyms: demesne, land. Examples: "His domain extended into europe." "He made it the law of the land."

(noun) (mathematics) the set of values of the independent variable for which a function is defined. Synonyms: domain of a function.

(noun) people in general; especially a distinctive group of people with some shared interest. Synonyms: world. Examples: "The western world."

(noun) the content of a particular field of knowledge. Synonyms: knowledge domain, knowledge base.