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 another symbol. In the case of a word, the word's definition often implies an intension. The term may also refer to all such intensions collectively, although the term comprehension is technically more correct for this.
The meaning of a word can be thought of as the bond between the idea the word means and the physical form of the word. Swiss linguist Ferdinand de Saussure (1857-1913) contrasts three concepts:
the signifier - the "sound image" or the string of letters on a page that one recognizes as the form of a sign,
the signified - the meaning, the concept or idea that a sign expresses or evokes,
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 in the Saussurean system, extension to the referent. Without intension of some sort, words have no meaning.
In philosophical arguments about dualism versus monism, it is noted that thoughts have intensionality and physical objects do not (S.E. Palmer, 1999), but rather have extension in space and time.
Note: 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.