A multigraph (or pleograph) is a sequence of letters that behaves as a unit and is not the sum of its parts, such as English ( ) or French (). The term is infrequently used, as the number of letters is usually specified:
Some multigraphs are considered ligatures, or letters unto themselves, such as in Dutch, in Hungarian, and in Serbo-Croatian and a few other Slavic languages.
Combinations longer than tetragraphs are unusual. The German pentagraph has largely been replaced by , remaining only in proper names such as or . Except for doubled trigraphs like German , hexagraphs are found only in Irish vowels, where the outside letters indicate whether the neighbouring consonant is "broad" or "slender". However, these sequences are not predictable. The hexagraph , for example, where the and mark the consonants as broad, represents the same sound (approximately the vowel in English write) as the trigraph , and with the same effect on neighbouring consonants.
Heptagraphs are extremely rare. Most fixed seven-letter sequences are composed of shorter multigraphs with a predictable result. The German sequence , used to transliterate Ukrainian , as in for "borscht", is a sequence of a trigraph and a tetragraph rather than a heptagraph. Likewise, the Juu languages have been claimed to have a heptagraph , but this is also a sequence, of and .
Beyond the Latin alphabet, Morse code uses hexagraphs for several punctuation marks, and the dollar sign is a heptagraph, . Longer sequences in Morse are considered ligatures, and transcribed as such in the Latin alphabet.