# Introduction to graphs

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## Introduction to graphs[edit]

A graph is a collection of nodes connected by edges. A graph is also frequently called a network, a node may be called a vertex, and an edge may be called a link. Commonly, a graph is denoted by an ordered pair , where is the set of nodes and is the set of edges.

Edges are the abstraction of some kind of relation between nodes, e.g. similarity, vicinity, communication, etc. We can distinguish directed and undirected edges.