ETYM French domaine, Old Fren. demaine, Latin dominium, property, right of ownership, from dominus master, owner. Related to Dame, and cf Demesne, Dungeon.
1. A knowledge domain that one is interested in or is communicating about; SYN. region, realm.
2. Territory over which rule or control is exercised; SYN. demesne, land.
3. The set of values of the independent variable for which a function is defined.

The set of all values that a database item can assume.
1. In database design and management, the set of valid values for a given attribute. For example, the domain for the attribute AREA-CODE might be the list of all valid three-digit numeric telephone area codes in the United States. See also attribute (definition 1).
2. For Windows NT Advanced Server, a collection of computers that share a common domain database and security policy. Each domain has a unique name.
3. In the Internet and other networks, the highest subdivision of a domain name in a network address, which identifies the type of entity owning the address (for example, .com for commercial users or .edu for educational institutions) or the geographical location of the address (for example, .fr for France or .sg for Singapore). The domain is the last part of the address (for example, www.acm.org). See also domain name.

Small area in a magnetic material that behaves like a tiny magnet. The magnetism of the material is due to the movement of electrons in the atoms of the domain. In an unmagnetized sample of material, the domains point in random directions, or form closed loops, so that there is no overall magnetization of the sample. In a magnetized sample, the domains are aligned so that their magnetic effects combine to produce a strong overall magnetism.