Diagraph (noun)
A drawing instrument that combines a protractor and scale.
Digraph (noun)
A directed graph.
Digraph (noun)
A two-character sequence used to enter a single conceptual character.
Digraph (noun)
A pair of letters, especially a pair representing a single phoneme.
Wiktionary
Digraph (noun)
a combination of two letters representing one sound, as in ph and ey.
Digraph (noun)
a character consisting of two joined letters; a ligature.
Oxford Dictionary