maths.free › Category Theory

Category Theory

Instead of asking what things are, ask how they map to each other. Category theory finds the same pattern — a product, a limit, an adjunction — recurring across every branch, and gives it one name.

Dersler

Symbols used here

F: \mathcal{C} \to \mathcal{D},\ \eta: F \Rightarrow G
functor, natural transformation
A structure-preserving map between categories; a map between functors.
\operatorname{Hom}(A, B),\ f \circ g
arrows from A to B, composition
The set of morphisms; do g then f.

Questions people ask

What is a functor?

A map between categories that sends objects to objects and arrows to arrows while respecting composition. Taking the fundamental group of a space is a functor from spaces to groups.

Diğer dallar