Realm

realm
1. A community or territory over which a sovereign rules; a kingdom.
2. A field, sphere, or province: the realm of science. See Synonyms at field.

3. (Government, Politics & Diplomacy) a royal domain; kingdom (now chiefly in such phrases as Peer of the Realm)
4. a field of interest, study, etc. the realm of the occult

Source

www.thefreedictionary.com