Hypertext Webster Gateway: "digraph"
From Webster's Revised Unabridged Dictionary (1913) (web1913)
Digraph \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.
From WordNet (r) 1.7 (wn)
digraph
n : two successive letters (especially two letters used to
represent a single sound: `sh' in `shoe')
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