Affection (linguistics)
Affection (also known as vowel affection, infection or vowel mutation), in the linguistics of the Celtic languages, is the change in the quality of a vowel under the influence of the vowel of the following final syllable. It is a type of anticipatory (or regressive) assimilation at a distance. The vowel that triggers the change was later normally lost. Some grammatical suffixes cause i-affection. In Welsh, gair "word" and -iadur "device suffix" yield geiriadur "dictionary", with -ai- in gair becoming -ei-.