In linguistics, lenition is a sound change that alters consonants, making them "weaker" in some way. The word lenition means 'softening' or 'weakening' (from Latin lēnis 'weak'). Lenition can happen both synchronically (within a language at a particular point in time) and diachronically (as a language changes over time). Lenition can involve such changes as voicing a voiceless consonant, causing a consonant to relax occlusion, to lose its place of articulation (a phenomenon called debuccalization, which turns a consonant into a glottal consonant like [h] or [ʔ]), or even causing a consonant to disappear entirely. An example of synchronic lenition is found in most varieties of American English, in the form of tapping: the /t/ of a word like wait [weɪt] is pronounced as the more sonorous [ɾ] in the related form waiting [ˈweɪɾɪŋ]. Some varieties of Spanish show debuccalization of /s/ to [h] at the end of a syllable, so that a word like estamos "we are" is pronounced [ehˈtamoh]. An example of diachronic lenition can be found in the Romance languages, where the /t/ of Latin patrem ("father", accusative) has become /d/ in Italian (an irregular change; compare saeta "silk" > seta) and Spanish padre (the latter weakened synchronically /d/ → [ð̞]), while in Catalan pare, French père and Portuguese pai historical /t/ has disappeared completely. 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 [ɡ]: "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 [ɡ] in y gath is thus caused by the syntax of the phrase, not by the modern phonological position of the consonant /k/. The opposite of lenition, fortition, a sound change that makes a consonant "stronger", is less common, but Breton and Cornish have "hard mutation" forms which represent fortition.
Types
Lenition involves changes in manner of articulation, sometimes accompanied by small changes in place of articulation. There are two main lenition pathways: opening and sonorization. In both cases, a stronger sound becomes a weaker one. Lenition can be seen as a movement on the sonority hierarchy from less sonorous to more sonorous, or on a strength hierarchy from stronger to weaker. In examples below, a greater-than sign indicates that one sound changes to another. The notation [t] > [ts] means that [t] changes to [ts]. The sound change of palatalization sometimes involves lenition. Lenition includes the loss of a feature, such as deglottalization, in which glottalization or ejective articulation is lost: [kʼ] or [kˀ] > [k]. The tables below show common sound changes involved in lenition. In some cases, lenition may skip one of the sound changes. The change voiceless stop > fricative is more common than the series of changes voiceless stop > affricate > fricative.
Opening In the opening type of lenition, the articulation becomes more open with each step. Opening lenition involves several sound changes: shortening of double consonants, affrication of stops, spirantization or assibilation of stops or affricates, debuccalization, and finally elision.
[tt] or [tː] > [t] (shortening, example in Greek) [t] > [ts] (affrication, for example Latin: terra to Aromanian: tsarã) [t] or [ts] > [s] (spirantization, example in Gilbertese language) [t̚] > [ʔ]; [s] > [h] (debuccalization, example in English or Spanish) [t], [ts], [s], [ʔ], [h] > ∅ (elision, for example Old French: feste to French: fête (cf. Spanish: fiesta))
Sonorization The sonorization type involves voicing. Sonorizing lenition involves several sound changes: voicing, approximation, and vocalization.
[t] > [d] (voicing, example in Korean) [d] > [ð] (approximation, example in Spanish) [d] > [i] (vocalization) Sonorizing lenition occurs especially often intervocalically (between vowels). In this position, lenition can be seen as a type of assimilation of the consonant to the surrounding vowels, in which features of the consonant that are not present in the surrounding vowels (e.g. obstruction, voicelessness) are gradually eliminated.
Some of the sounds generated by lenition are often subsequently "normalized" into related but cross-linguistically more common sounds. An example would be the changes [b] → [β] → [v] and [d] → [ð] → [z]. Such normalizations correspond to diagonal movements down and to the right in the above table. In other cases, sounds are lenited and normalized at the same time; examples would be direct changes [b] → [v] or [d] → [z].
Vocalization L-vocalization is a subtype of the sonorization type of lenition. It has two possible results: a velar approximant or back vowel, or a palatal approximant or front vowel. In French, l-vocalization of the sequence /al/ resulted in the diphthong /au/, which was monophthongized, yielding the monophthong /o/ in Modern French.
Mixed Sometimes a particular example of lenition mixes the opening and sonorization pathways. For example, [kʰ] may spirantize or open to [x], then voice or sonorize to [ɣ]. Lenition can be seen in Canadian and American English, where /t/ and /d/ soften to a tap [ɾ] (flapping) when not in initial position and followed by an unstressed vowel. For example, both rate and raid plus the suffix -er are pronounced [ˈɹeɪ̯ɾɚ]. The Italian of Central and Southern Italy has a number of lenitions, the most widespread of which is the deaffrication of /t͡ʃ/ to [ʃ] between vowels: post-pausal cena [ˈt͡ʃeːna] 'dinner' but post-vocalic la cena [laˈʃeːna] 'the dinner'; the name Luciano, although structurally /luˈt͡ʃano/, is normally pronounced [luˈʃaːno]. In Tuscany, /d͡ʒ/ likewise is realized [ʒ] between vowels, and in typical speech of Central Tuscany, the voiceless stops /p t k/ in the same position are pronounced respectively [ɸ θ x/h], as in /la kasa/ → [laˈhaːsa] 'the house', /buko/ → [ˈbuːho] 'hole'.
Effects
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