metaphony
in historical linguistics, assimiliation between vowels in a word, typically separated by several consonants or syllables
umlaut
metaphony in which a vowel is pronounced more like a following vowel or semivowel
Germanic a-mutation
metaphonic process in late Proto-Germanic (c. 200)
affection
anticipatory metaphony in Celtic languages: e.g. Welsh gair → geiriadur
i-mutation
vowel sound change