Introduction
“The slogan is ‘Adjoint functors arise everywhere’.” (Saunders Mac Lane, Categories for the working mathematician)
The long list of examples in this article is only a partial indication of how often an interesting mathematical construction is an adjoint functor. As a result, general theorems about left/right adjoint functors, such as the equivalence of their various definitions or the fact that they respectively preserve colimits/limits (which are also found in every area of mathematics), can encode the details of many useful and otherwise non-trivial results.
Read more about this topic: Adjoint Functors
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