Page "Preorder" Paragraph 17

* Every finite topological space gives rise to a preorder on its points, in which x ≤ y if and only if x belongs to every neighborhood of y, and every finite preorder can be formed as the specialization preorder of a topological space in this way.

That is, there is a 1-to-1 correspondence between finite topologies and finite preorders.

However, the relation between infinite topological spaces and their specialization preorders is not 1-to-1.