👉 In computer science and graph theory, a preorder is a binary relation on a set S that preserves order. It means that for all x, y in S, if x < y then z < w implies x < w. In other words, if we have two elements a and b, then a < b holds only if there exists an element c such that a < c < b. For example, the preorder ≤ on the set of integers {1, 2, 3} is
