|This article does not cite any references or sources. (June 2011)|
In mathematics, specifically in category theory, an extranatural transformation is a generalization of the notion of natural transformation.
Let and two functors of categories. A family is said to be natural in a and extranatural in b and c if the following holds:
- is a natural transformation (in the usual sense).
- (extranaturality in b) , , the following diagram commutes
- (extranaturality in c) , , the following diagram commutes