1. the total system of ideas, concepts, terms, and expressions within which a given topic can be analyzed and understood. The universe of discourse defines both what can be said about a subject and how it can be said. Statements that are meaningful within a particular universe of discourse may well be nonsensical within another; to say The sad skies are weeping, for example, might be permissible in poetry but would not be so in meteorology. The idea of universes of discourse has also been explored by radical thinkers in the traditions of Marxism, feminism, and poststructuralism; such critics argue that by controlling the universe of discourse in a particular society, the power elite controls what can and cannot be said or thought.

2. in the field of artificial intelligence, any set of objects that can be represented within a given domain.