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Not to be confused with the homophone intention; or the related concept of intentionality. For the song "Intension" by Tool, see 10,000 Days.

In linguistics, logic, philosophy, and other fields, an intension is any property or quality connoted by a word, phrase or other symbol. In the case of a word, it is often implied by its definition. The term may also refer to the complete set of meanings or properties that are implied by a concept, although the term comprehension is technically more correct for this.

Intension is generally discussed with regard to extension (or denotation). Intension refers to the set of all possible things a word or phrase could describe, extension to the set of all actual things the word describes. For example, the intension of a car is the all-inclusive concept of a car, including, for example, mile-long cars made of chocolate that may not actually exist. But the extension of 'car' is all actual instances of cars (past, present, and future), which will amount to millions or billions of cars, but probably does not include any mile-long cars made of chocolate.

The meaning of a word can be thought of as the bond between the idea or thing the word refers to and the word itself. Swiss linguist Ferdinand de Saussure contrasts three concepts:

• the signified — the concept or idea that a sign evokes.
• the signifier — the "sound image" or string of letters on a page that one recognizes as a sign.
• the referent — the actual thing or set of things a sign refers to. See Dyadic signs and Reference (semantics).

Intension is analogous to the signified, extension to the referent. The intension thus links the signifier to the sign's extension. Without intension of some sort, words can have no meaning.

Intension and intensionality (the state of having intension) should not be confused with intention and intentionality, which are pronounced the same and occasionally arise in the same philosophical context. Where this happens, the letter 's' or 't' is sometimes italicized to emphasize the distinction.

• Comprehension
• Description Logic
• Intensional definition
• Intensional statement

• Ferdinand De Saussure: Course in General Linguistics. Open Court Classics, July 1986. ISBN 0-812-69023-0