1. a visual representation of the relationship between numbers or quantities, which are plotted on a drawing with reference to axes at right angles (see x-axis; y-axis) and linked by lines, dots, or the like. Bar graphs, histograms, and frequency polygons are commonly used examples.

2. in computer programming, a data structure consisting of a set of nodes (not necessarily finite in number) and a set of arcs that connect pairs of nodes. In a directed graph, the arcs have a unique direction from one node (the parent) to the other node (the child). The set of child nodes of one parent are called siblings of each other. A path is a sequence of connected parent–child arcs, in which each child in the sequence is also a parent of the next state in the sequence. A rooted graph has a unique node from which all paths in the graph originate. A tip node or leaf node in the graph is a node without children. The graph structure is often used for representing search in games or other situations of problem solving or for capturing relationships, as in semantic networks. See also tree.