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Extension (logic)

Refers to the totality of all objects described by a particular term.

For example, the extension of the term “horse” could be defined as follows:

“Horse” describes all animals of the genus Equidae.

In other contexts, the same term may have a different extension:

The term “horse” describes all the chess pieces also known as “knights”.

The opposite term to extension is intension, which describes the definition of a term by its associated meanings.



As the examples above show, the same identifier can describe different sets of terms depending on the context. It is therefore generally important to understand the precise extension of a term in order to avoid possible errors of equivocation.


Ambiguity of the extension of a term can also result from the grammatical structure of a statement ( amphiboly). See also: Syntactic ambiguity.

See also

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Ad Hominem Info is a project to explain and categorize the most common systematic fallacies and fallacies. On this page, you will find a background article that briefly explains an important logical concept, which may be needed to better understand another article in this area.
For more information, please see the main category “logic

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