1) A trigraph is a three-character replacement for a special or nonstandard character in a text file. A trigraph can be used in place of a symbol that is not present on a keyboard or in a character set. However, some programs cannot properly interpret them.
The following table denotes the most commonly encountered trigraphs in computer applications.
2) In some security applications, groups of three characters are used as code words to represent specific processes, people, programs, systems, or other entities. Such character triplets are known as trigraphs.
3) In a written language, a trigraph is a set of three consecutive letters that represents a single sound. For example, in the term "weather bureau," the letters e, a, and u together represent a long "o" sound, as in "oh."