In any of several fields of study that treat the use of signs—for example, in linguistics, logic, mathematics, semantics, semiotics, and philosophy of language—an intension is any property or quality connoted by a word, phrase, or another symbol.
For instance, the intensions of the word plant include properties such as "being composed of cellulose (not always true)", "alive", and "organism", among others.
Swiss linguist Ferdinand de Saussure (1857–1913) contrasts three concepts: Without intension of some sort, a word has 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.
A statement-form is simply a form obtained by putting blanks into a sentence where one or more expressions with extensions occur—for instance, "The quick brown ___ jumped over the lazy ___'s back."
It should be clear that no matter what is put for "Mark Twain", so long as it is a singular term picking out the same man, the statement remains true.