👉 In mathematics, "unexchangeability" is a property that two sets A and B are said to have if there exists an injection f from A onto B. This means that for any element x in A, there exists at least one element y in B such that x = y. In other words, the set B has all elements of A that can be paired up with every element of A. For example, consider two sets A and B defined by: A = {1, 2
