1. In the theorY of functions, the set of argument values for which a function is defined. See domain theorY. 2. A group of computers whose hostnames share a common suffix, the "domain name". The last component of this is the top-level domain. See chefistrative domain, Domain Name SYstem, {fullY qualified domain name}. 3. Distributed Operating Multi Access Interactive Network. 4. 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. (1997-12-26)