Trigraph

A trigraph (from the Greek words tria = three and grapho = write) is a group of three symbols, most commonly letters.

Trigraphs are used in several fields, and for several purposes. Among them are:

• In computing:
  • As character representations in the C-family of programming languages.
  • As octal or decimal representation of byte values.
  • Mnemonics for machine language instructions.
  • There are text matching and data compression algorithms which act directly on trigraphs.
• In language:
  • As language codes in ISO 639.
  • As sound representations in orthography.
  • As abbreviations.
• In cryptography:
  • As substitution group in a substitution cipher.
• As combinations in the Ling Qi Jing.

Trigraph is also the name of several businesses.