Affection (linguistics) in the context of "Umlaut (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 assimilation, or, more specifically, anticipatory (or regressive) assimilation at a distance.

The two main types of affection are a-affection and i-affection. There is also u-affection, which is more usually referred to as u-infection. I-affection is an example of i-mutation and may be compared to the Germanic umlaut, and a-affection is similar to Germanic a-mutation. More rarely, the term "affection", like "umlaut", may be applied to other languages and is then a synonym for i-mutation generally.