In historical linguistics, metaphony is a class of sound change in
which one vowel in a word is influenced by another in a process of
assimilation. The sound change is normally "long-distance" in that the
vowel triggering the change may be separated from the affected vowel
by several consonants, or sometimes even by several syllables.
For more discussion, see the article on vowel harmony.
There are two types:
Progressive (or left-to-right) metaphony, in which a vowel early in
the word influences a subsequent vowel.
Regressive (or right-to-left) metaphony, in which a vowel towards the
end of the word influences a preceding vowel.
Metaphony is closely related to some other linguistic concepts:
Vowel harmony is sometimes used synonymously with metaphony. Usually,
however, "vowel harmony" refers specifically to a synchronic process
operating in a particular language, normally requiring all vowels in a
word to agree in a particular feature (e.g. vowel height or vowel
backness). Most commonly, the triggering vowel is in the first
syllable of the word (i.e. this is a type of progressive metaphony),
as in Turkish, Finnish or Hungarian. In some cases, however, the
triggering vowel is in the last syllable, typically a suffix, as in
many varieties of Andalusian Spanish.
Umlaut refers to regressive metaphony, usually specifically of a
diachronic type operating in the history of a language. The term
"umlaut" is found especially in the
Germanic languages (see Germanic
umlaut). In some other languages, other terms are used instead for the
same process (e.g. affection in Old Irish, simply metaphony in the