The definition of a set by enumerating its members. An extensional definition can always be reduced to an intentional
one.

An extension field is sometimes also called simply
an extension.

## See also

Extension Field,

Intension
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## References

Russell, B. "Definition of Number." *Introduction to Mathematical Philosophy.* New York: Simon and Schuster, 1971.## Referenced
on Wolfram|Alpha

Set Extension
## Cite this as:

Weisstein, Eric W. "Set Extension." From
*MathWorld*--A Wolfram Web Resource. https://mathworld.wolfram.com/SetExtension.html

## Subject classifications