domain

In physics, 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.

domain

In mathematics, base set of numbers on which a function works, mapping it on to a second set (the range).

domain

On the Internet, segment of an address that specifies an organization, its type, or its country of origin. All countries except the USA use a final two-letter code such as ca for Canada and uk for the UK. A us suffix exists for the USA, but is not widely used. US addresses usually end in one of seven ‘top-level’ domains, which specify the type of organization: com (commercial), mil (military), org (usually a nonprofit-making organization), and so on. In 2006 there were more than 80 million domain names registered on the Internet.

The domain names are for the benefit of humans; to enable mail and other messages to be sorted by machine, computers use IP (Internet protocol) numbers. To route a message, the computer looks up the domain name on a domain name server (DNS), which tells the computer the number.

In 1999, the US Government handed over responsibility for the top-level domain names com, org, and net from the private company Network Solutions Inc (NSI) to the non-commercial organization ICANN.