information:highlighting, structural:reformatting
Graph theory

In graph theory, the Cartesian product of two graphs G and H is the graph denoted by G × H, whose vertex set is the (ordinary) Cartesian product V (G) × V (H) and such that two vertices (u, v) and (u ′, v ′) are adjacent in G × H, if and only if u = u ′ and v is adjacent with v ′ in H, or v = v ′ and u is adjacent with u ′ in G. The Cartesian product of graphs is not a product in the sense of category theory. Instead, the categorical product is known as the tensor product of graphs.