1. <mathematics> In the theory of functions, the set of argument values for which a function is defined.
See domain theory.
2. <networking> A group of computers whose hostnames share a common suffix, the "domain name". The last component of this is the top-level domain.
See administrative domain, Domain Name System, fully qualified domain name.
3. Distributed Operating Multi Access Interactive Network.
4. <programming> A specific phase of the software life cycle in which a developer works. Domains define developers' and users' areas of responsibility and the scope of possible relationships between products.
5. The subject or market in which a piece of software is designed to work.