Trinode

Trinode is a term used in several disciplines to denote a structure involving three nodes or connections. Because it is not standardized, its exact meaning depends on the field of study. In graph theory, a trinode most commonly refers to a vertex of degree three—the point of a graph where three edges meet. In many networks, such a node acts as a local junction or branching point, linking three distinct paths. When describing rooted trees and other hierarchical structures, a trinode may be described as an internal node with three incident edges, though conventions vary on whether the parent edge is counted.

Outside pure graph theory, the word trinode appears less formally. In some contexts it is used to describe three-way junctions in circuit diagrams or transport networks, and occasionally in materials science or chemistry literature as a loose shorthand for a three-coordinate center. However, these uses are not universal, and more precise terms like three-valent, tri-coordinate, or tri-armed are often preferred in those fields.

Examples include a vertex connected to three neighbors in a simple undirected graph, or a three-armed junction in a schematic diagram. The term evokes the idea of three branches meeting at a single point, and it is most productive when its meaning is clarified by the surrounding context.

Etymology and related terms: the word combines tri-, meaning three, with node, meaning a point of connection. See also node, degree, valence, branching point, and trifurcation.