Definition 3

Let G be a graph and X a set. The set of all objects which correspond under G to elements of X is called the image of X under G and is denoted by $G\langle X \rangle$ or $G(X)$.

¶ Let $\Gamma = (G, A, B)$ be a correspondence and let X be a subset of A. The set $G\langle X \rangle$ is also denoted by $\Gamma\langle X \rangle$ or $\Gamma(X)$ and is called the image of X under $\Gamma$.

Remarks