In graph theory, one area of study concerns the possibility of travelling around a graph, going along edges in such a way as to visit every vertex exactly once. A Hamiltonian cycle is a cycle that contains every vertex, and a graph is called Hamiltonian if it has a Hamiltonian cycle. The term arises from Hamilton’s interest in the existence of such cycles in the graph formed from the dodecahedron’s vertices and edges. Compare eulerian graph.