# Graph (mathematics)

In mathematics, a graph is used to show how things are connected. The things being connected are called vertices, and the connections among them are called edges. If vertices are connected by an edge, they are called adjacent. The degree of a vertex is the number of edges that connect to it. A graph's size ${\displaystyle |E|}$is the number of edges in total. The number of vertices, written as ${\displaystyle |V|}$, is called the order of a graph.