Tone sandhi

Tone sandhi is a phonological change occurring in tonal languages, in which the tones assigned to individual words or morphemes change based on the pronunciation of adjacent words or morphemes. It usually simplifies a bidirectional tone into a one-direction tone. It is a type of sandhi, or fusional change, from the Sanskrit word for "joining".

Tone sandhi occurs to some extent in nearly all tonal languages, manifesting itself in different ways. Tonal languages, characterized by their use of pitch to affect meaning, appear all over the world, especially in the Niger-Congo language family of Africa, and the Sino-Tibetan language family of East Asia, as well as other East Asian languages such as Tai-Kadai, Vietnamese, and Papuan languages. Tonal languages are also found in many Oto-Manguean and other languages of Central America, as well as in parts of North America (such as Athapaskan in British Columbia, Canada), and Europe.

Many North American and African tonal languages undergo "syntagmatic displacement," as one tone is replaced by another in the event that the new tone is present elsewhere in the adjacent tones. Usually, these processes of assimilation occur from left to right. In the Bantu languages of West Africa, for example, an unaccented syllable takes the tone from the closest tone to its left. However, in East and Southeast Asia, "paradigmatic replacement" is a more common form of tone sandhi, as one tone changes to another in a certain environment, whether or not the new tone is already present in the surrounding words or morphemes.

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