do·main 
(dō-mān)
(dō-mān)n.
1. A territory over which rule or control is exercised.
2. A sphere of activity, influence, or knowledge: the domain of history. See Synonyms at field.
3. 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.
4. Computers A group of networked computers that share a common communications address.
5. 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.
6. Biology Any of three primary divisions of organisms, consisting of the eukaryotes, bacteria, and archaea, that rank above a kingdom in taxonomic systems based on similarities of DNA sequences.
7. Law The land of one with paramount title and absolute ownership.
[French domaine, blend of Old French demaine (from Late Latin dominicum) and Latin dominium, property, both from dominus, lord; see dem- in the Appendix of Indo-European roots.]