Three letters united in pronunciation so as to have but one sound, or to form but one syllable, as -ieu in adieu; a triphthong.

In the C and C++ languages, a sequence of three characters, the first two of which are question marks. Before any other processing takes place, the trigraph is replaced by a corresponding single character. Trigraphs are used to represent characters that are reserved as control characters. See control character, digraph.

Sequence of three letters which represent a single phoneme. Example: for /ò/, sch in German.

a combination of three letters representing one sound

a sound with three syllables

a three character sequence that is replaced by a corresponding single character

a three-letter string, such as abc or bcd

A three-letter sequence representing a single consonant, vowel, or diphthong, such as EAU in BEAU.

A trigraph (from the Greek words treis = three and graphein = write) is a group of three letters used to represent a single sound or a combination of sounds that does not correspond to the written letters combined. For example, in the word schilling, the trigraph "sch" represents the sound of "sh". In the word "night", "igh" represents the vowel (IPA: ) (a diphthong).