A multigraph (or pleograph) is a sequence of letters that behaves as a unit and is not the sum of its parts, such as English ⟨ch⟩ or French ⟨eau⟩.

In mathematics, and more specifically in graph theory, a multigraph is a graph which is permitted to have multiple edges (also called parallel edges), that is, edges that have the same end nodes. Thus two vertices may be connected by more than one edge.

A phoneme may be represented by a sequence of letters, called a multigraph, rather than by a single letter (as in the case of the digraph ch in French and the trigraph sch in German), that retains predictability only if the multigraph cannot be broken down into smaller units.