Definitions for: Digraph

[n] two successive letters (especially two letters used to represent a single sound: `sh' in `shoe')

Webster (1913) Definition: Di"graph, n. [Gr. di- = di`s- twice + ? a writing, ?
to write.]
Two signs or characters combined to express a single
articulated sound; as ea in head, or th in bath.

See Also: alphabetic character, letter, letter of the alphabet