Linked from
The 10 pages that link to Category, each with the reason it gives.
Category theoryBroader topic: This is the basic structure category theory studies.
MonoidRelated: A monoid is exactly a category with one object.
MorphismRelated: A category specifies which morphisms exist and how they compose.
Yoneda lemmaBroader topic: The theorem is stated for objects and morphisms belonging to a category.