Let π be a topological space, and π«π be its path algebra.
The following congruence relation on paths makes π«π into a Small categoryππ.
Let πΌ,π½βπ«π(π₯,π¦).
Then πΌβΌπ½ iff πΌ=π½βπ for some πβπ³ππ(π,π).
The category ππ=π«π/βΌ is called the category of paths on π.