In mathematics, a skeleton of a category is a subcategory that, roughly speaking, does not contain any extraneous isomorphisms.
In a certain sense, the skeleton of a category is the "smallest" equivalent category, which captures all "categorical properties" of the original.
In fact, two categories are equivalent if and only if they have isomorphic skeletons.
A category is called skeletal if isomorphic objects are necessarily identical.
[citation needed] (This is equivalent to the axiom of choice.)