Functions, One-to-One, and Onto

Abstract

Functions can map elements from the domain to the codomain in many ways. A function may “hit” every element in the codomain, or it may “miss” some. It may assign more than one x to a y or it may assign exactly one x to each y. We will understand our function better if we know which of these things it does. Precise formulations of these ideas will be given in a moment. It’s a mouthful, though, and really requires practice.