Definition

Definition is a statement that assigns the meaning of a term or a phenomenon by specifying its essential properties and delimiting its scope. In philosophy, linguistics, and logic, definitions aim to capture what a word or concept denotes and to distinguish it from others.

Historically, definitions have taken many forms. Lexical definitions describe common usage (dictionary entries); stipulative definitions set or fix a meaning for a term in a particular context; precising definitions attempt to reduce vagueness; theoretical definitions express an essential property within a theory; ostensive definitions point to examples or instances.

A traditional approach is genus and difference: a definition states the broader category (genus) and what makes the term distinct (difference). For example, a triangle is a plane figure with three sides; this combines a genus (plane figure) and a differentiating feature (three sides). In mathematics and formal sciences, definitions specify necessary and sufficient conditions that uniquely identify an object or concept.

Good definitions are typically clear, true, non-circular, and useful, aiming for precision without being overly restrictive. They avoid circularity where the term to be defined appears in its own definition. Definitions can be revised as theories evolve or usage shifts.

Applications include dictionaries, legal texts, scientific terminology, and philosophical analysis. By providing a precise account of meaning, definitions enable communication, argument, and the development of knowledge.