範疇論係數學入面嘅一科，用好抽象嘅方法嚟處理唔同嘅數學概念，將唔同嘅概念形式化做「物件」同埋「態射」。數學入面好多嘅領域都有對應嘅範疇，例如微分幾何就有「可微流形範疇」，物件係「可微流形」，態射就係「光滑映射」。用範疇論可以令唔同領域入面嘅數學結論更加容易論述、證明，而且可以搵到唔同領域之間嘅關係。
Category theory is a discipline in mathematics that uses abstract methods to deal with different mathematical concepts, formalizing different concepts into "objects" and "morphism". Many fields in mathematics have corresponding categories, for example, differential geometry has a "micromanifold category", objects are "micromanifolds", and morphism is "smooth mapping". The use of category theory can make it easier to discuss and prove mathematical conclusions in different fields, and to find the relationship between different fields.