What is a vertex in a graph?

A vertex is the basic element of a graph that represents an object, point, or entity.

Vertices are nodes that connect to each other via edges.

Example:

• In a road graph, vertices are cities.
• In a social network, vertices are users.
• In a computer network, vertices are devices or servers.

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Properties of a vertex:

• Can have an identifier (a number, a name).
• Can hold data (for example, a weight, a label, coordinates).
• Can be connected to other vertices via edges.

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Types of vertices:

• Isolated - not connected to any other vertex.
• Adjacent - has at least one edge leading to another vertex.

Summary: a vertex is a "point", and edges are the "lines" that connect these points, forming the structure of a graph.