What does definition mean?
A definition is a precise statement of the meaning of a word, phrase, or concept, most familiarly encountered in dictionaries but equally essential in law, science, mathematics, and philosophy, where clarity about terms underpins every argument. Beyond this core sense, 'definition' also names the act of defining itself — the intellectual work of drawing boundaries around an idea so that it can be discussed with precision. A third, more modern usage appears in technology: 'high definition' describes images whose outlines and details are rendered sharply and distinctly. The word carries connotations of rigor, clarity, and authority; to offer a definition is to claim command over a subject's limits. Common phrases such as 'by definition,' meaning necessarily or intrinsically, show how deeply the notion is woven into reasoning itself. Whether fixing the sense of a single word or the resolution of a screen, definition remains one of language's most fundamental tools for turning vagueness into understanding.
nounA statement of the exact meaning of a word, phrase, or term, especially as given in a dictionary; also, the act or process of making something clear or distinct.
- A statement giving the exact meaning of a word, phrase, or concept.
- The act, process, or power of defining — of stating clearly or making distinct.
- The degree of distinctness or sharpness in outline or detail, as in an image (e.g. high-definition).
"The dictionary's definition of 'serendipity' captures its sense of fortunate discovery."
"Her essay opened with a careful definition of the key term at issue."
"The new camera records video in stunning high definition."
Regular plural; used when referring to multiple statements of meaning, as across different dictionaries or within a technical document.
"The two dictionaries offer strikingly different definitions of the same word."
By definition, a definition can never fully define itself — which is why lexicographers call dictionary writing 'the impossible craft.'
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of definition
'Definition' entered English in the late Middle Ages, borrowed via Old French from Latin definitio, meaning a setting of bounds or limits. The noun derives from definire, formed from de- (indicating completion) plus finire ('to limit, set bounds'), which itself comes from finis, 'boundary' or 'end.' This same root gives English a whole family of related words — finite, definite, finish, and refine — all sharing the underlying idea of an edge or terminus. The verb 'define' was established in English somewhat before the noun became common in scholarly use.
Related word forms
How definition is actually used
Neutral register, suitable for both formal academic prose and everyday speech. In philosophy and mathematics, the plural 'definitions' often refers to formal statements within a text. The phrase 'by definition' signals that something follows necessarily from a term's meaning rather than from evidence.
Easily confused with definition
A description portrays what something is like in general terms, while a definition states precisely and authoritatively what something means or is.
An explanation clarifies how or why something happens, whereas a definition fixes the meaning or boundaries of a term.