A data structure consisting of nodes connected to other nodes with edges

• Order: The number of vertices in the graph
• Size: The number of edges in the graph
• Vertex degree: The number of edges that are incident to a vertex
• Isolated vertex: A vertex that is not connected to any other vertices in the graph
• Self-loop: An edge from a vertex to itself
• Directed graph: A graph where all the edges have a direction indicating what is the start vertex and what is the end vertex
• Undirected graph: A graph with edges that have no direction
• Weighted graph: Edges of the graph has weights
• Unweighted graph: Edges of the graph has no weights