Lenition

In linguistics, lenition is a kind of sound change that alters consonants, making them more sonorous. The word lenition itself means "softening" or "weakening" (from Latin lenis = weak). Lenition can happen both synchronically (i.e., within a language at a particular point in time) and diachronically (i.e. as a language changes over time). Lenition can involve such changes as making a consonant more sonorous (vowel-like), causing a consonant to lose its place of articulation (a phenomenon called debuccalization, which turns a consonant into a glottal consonant like or ), or even causing a consonant to disappear entirely.

An example of synchronic lenition in English is found in flapping in some dialects: the /t/ of a word like wait becomes the more sonorous in the related form waiting . Some dialects of Spanish show debuccalization of /s/ to at the end of a syllable, so that a word like estamos "we are" is pronounced . An example of diachronic lenition can be found in the Romance languages, where the /t/ of Latin patrem ("father", accusative) becomes in Italian padre and in Spanish padre, while in French père and Portuguese pai it has disappeared completely. Along with assimilation, lenition is one of the primary sources of phonological change of languages.

In some languages, lenition has been grammaticalized into a consonant mutation, which means it is no longer triggered by its phonological environment but is now governed by its syntactic or morphological environment. For example, in Welsh, the word cath "cat" begins with the sound /k/, but after the definite article y, the /k/ changes to : "the cat" in Welsh is y gath. This was historically due to intervocalic lenition, but in the plural, lenition does not happen, so "the cats" is y cathod, not *y gathod. The change of /k/ to in y gath is thus caused by the syntax of the phrase, not by the phonological position of the consonant /k/.

The opposite of lenition is fortition, a sound change making a consonant "stronger".