(mathematics, physics) A system which is time-dependent.

dynamical system

(physics) A system that does not interact with its surroundings. Depending on context this may mean that its total energy and/or momentum stay constant. In thermodynamics, isolated is usually used to indicate that the system's energy does not change. In mechanics it is used to indicate that the system's momentum does not change.

(physics, chemistry, engineering) A physical system whose interaction with its environment is limited to particular types of transfer, so that certain quantities are conserved within the system.

(logic) A formal system.

(logic) The grouping of a formal language and a set of inference rules and/or axioms.

(ethics) A particular set of consistent ethical principles.

(artificial intelligence) A type of artificially intelligent software system, which stores expertise concerning some subject matter in a knowledge base and attempts to answer questions or solve problems in a manner which simulates the thought processes of a human expert.

(computing) An old computer system or application program that continues to be used because the user (typically an organization) does not want to replace or redesign it.

(computing) A computer system with a dedicated function within a larger mechanical or electrical system, often with real-time computing constraints.