Selfdescriptive

Selfdescriptive is an adjective used to describe something that describes itself or its own properties. In common usage, it applies to statements, descriptions, or data that reveal aspects of the subject without external comparison. The term is often encountered in discussions of language and logic, where self-reference is a central concern.

Linguistics: The related notion autological describes words that express a property they themselves possess. When a word describes its own form, meaning, or length, it is sometimes considered self-descriptive. Examples commonly cited include 'polysyllabic' (the word itself is polysyllabic) and 'sesquipedalian' (a long word). By contrast, 'monosyllabic' is not self-descriptive, as the word is multisyllabic.

Self-descriptive numbers: In recreational mathematics, a self-descriptive number in base b is a b-digit number where the digit in position i encodes the number of occurrences of i among the digits. In base 10, one famous example is 6210001000, which contains six 0s, two 1s, one 2, and zeros for other digits until a single 6 appears. More generally, such numbers exist in various bases.

Other uses: The term can describe self-descriptive data sets or self-describing metadata, where the content includes its own descriptive attributes (for example, a dataset header that records its own structure).

See also autological, heterological, self-reference, self-descriptive number.