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Vertex
In graph theory, a vertex V (also called node or point) is the fundamental unit of which graphs are formed.
Explanation
In a diagram of a graph, a vertex is usually represented by a circle with a label, and an edge is represented by a line extending from one vertex to another.
A graph with 6 vertices and 7 edges
An undirected graph consists of a set of vertices and a set of edges (unordered pairs of vertices), while a directed graph consists of a set of vertices and a set of arcs (ordered pairs of vertices).