# Range of values

The set of all elements which a given function puts into correspondence with the elements of its domain of definition; that is, if $f : X \rightarrow Y$, then the set of values of $f$ is the set $Y_f$ of all $y \in Y$ for which there exists an $x \in X$ with $f(x) = y$. Thus, the range of values of a function is the image of its domain of definition, $Y_f = f(X)$.