Domain of a function

The domain of a function is the set of inputs the function accepts, sometimes written as dom of f where f is the function; informally, the domain can be thought of as everything the input variable is allowed to be. More precisely, for a function f mapping a set X to a set Y, the domain of f is the set X itself, and in modern mathematical language the domain is considered part of the very definition of the function rather than merely a property of it. When X and Y are both sets of real numbers, the function can be graphed on the Cartesian plane, with the domain appearing along the horizontal axis as the projection of the graph onto that axis, while the set Y is called the codomain and the actual set of outputs the function produces is called its range or image. Any function can also be restricted to a subset of its domain, producing a new function defined only on that smaller set. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/