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".

Read more about Lenition:  Common Characteristics, Sound Changes Associated With Lenition, Diachronic Lenition, Consonant Gradation, Fortition

Other articles related to "lenition":

Scottish Gaelic Phonology - Consonants - Lenition and Spelling
... Lenition changes Radical Lenited Broad Slender Orthography Broad Slender b bh c ch d dh f fh silent g gh l† m mh n† p ph r† s sh t th ^† Lenition of initial l n r is not shown in writing ... Lenition may be blocked when homorganic consonants (i.e ... those made at the same place of articulation) clash with grammatical lenition rules ...
Irish Initial Mutations - Lenition - Environments of Lenition - In Head + Modifier Constructions
... aimsir bháistí "rainy weather" (lenition after a feminine singular noun) buidéil shú "bottles of juice" (lenition after a plural ending in a slender consonant ...
Lenition - Fortition
... one considered "strong" – the opposite of lenition ... Although less frequent than lenition in the languages of the world, word-initial and word-final fortition is not uncommon ...
Orphan Initialism - Non-English Language - Lenition
... In languages such as Scottish Gaelic and Irish, where lenition (initial consonant mutation) is commonplace, acronyms must also be modified in situations where case ...