domain

A domain is the area a given person or people rules or an area of knowledge. (noun)

See domain in Webster's New World College Dictionary

noun

territory under one government or ruler; dominion
land belonging to one person; estate
supreme ownership
field or sphere of activity or influence: the domain of science
Comput. domain name
Math.
1. the set of those values of an independent variable which exist for a given function
2. the set of all integers, or a set of elements which can be combined in the same way as the integers
Physics a region in a ferromagnetic material within which the atoms are magnetically aligned: alignment of these regions results in the material being magnetized

See domain in American Heritage Dictionary 4

(dō-mānˈ)

noun

A territory over which rule or control is exercised.
A sphere of activity, concern, or function; a field: the domain of history. See Synonyms at field.
Physics Any of numerous contiguous regions in a ferromagnetic material in which the direction of spontaneous magnetization is uniform and different from that in neighboring regions.
Law
a. The land of one with paramount title and absolute ownership.
b. Public domain.
Mathematics
a. The set of all possible values of an independent variable of a function.
b. An open connected set that contains at least one point.
Biology Any of three primary divisions of living systems, consisting of the eukaryotes, bacteria, and archaea, that rank above a kingdom in taxonomic systems that are based on similarities of DNA sequences.
Computer Science A group of networked computers that share a common communications address.