digram

from WordNet (r) 3.0 (2006)

digram
    n 1: two successive letters (especially two letters used to
         represent a single sound: `sh' in `shoe') [syn: {digraph},
         {digram}]

from The Collaborative International Dictionary of English v.0.48

Digram \Di"gram\, n. [Gr. di- = di`s- twice + ? letter.]
   A digraph.
   [1913 Webster]

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