Definition of "digraph" [di•graph]

• A pair of letters representing a single speech sound, such as the ph in pheasant or the ea in beat. (noun)
• A single character consisting of two letters run together and representing a single sound, such as Old English æ. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Digraphs: The digraph is a two-letter "country code" that precisely identifies every entity without overlap, duplication, or omission."
• "A digraph is a union of two vowels, or of two consonants, in one sound."
• "Thus, the center of a digraph is a vertex that is closest to the vertex most distant from it."