Lenition

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)
• [t] > [ts] (affrication, for example Latin: terra to Aromanian: tsarã)
• [t] or [ts] > [s] (spirantization, example in Gilbertese language)
• [t] > [ʔ]; [s] > [h] (debuccalization, example in English or Spanish)
• [t], [ts], [s], [ʔ], [h] > ∅ (elision)

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].

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.

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]. In many British English dialects, a different lenition that affects only [t] takes place: [t] > [ʔ] (see T-glottalization). 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'.

Diachronic lenition is found, for example, in the change from Latin into Spanish, in which the intervocalic voiceless stops [p t k] first changed into their voiced counterparts [b d ɡ], and later into the approximants or fricatives [β̞ ð̞ ɣ̞]: vita > vida, lupa > loba, caeca > ciega, apotheca > bodega. One stage in these changes goes beyond phonetic to have become a phonological restructuring, e.g. /lupa/ > /loba/ (compare /lupa/ in Italian, with no change in the phonological status of /p/). The subsequent further weakening of the series to phonetic [β̞ ð̞ ɣ̞], as in [loβ̞a] is diachronic in the sense that the developments took place over time and displaced [b, d, g] as the normal pronunciations between vowels. It is also synchronic in an analysis of [β̞ ð̞ ɣ̞] as allophonic realizations of /b, d, g/: illustrating with /b/, /bino/ 'wine' is pronounced [bino] after pause, but with [β̞] intervocalically, as in [de β̞ino] 'of wine'; likewise, /loba/ → [loβ̞a].

A similar development occurred in the Celtic languages, where non-geminate intervocalic consonants were converted into their corresponding weaker counterparts through lenition (usually stops into fricatives but also laterals and trills into weaker laterals and taps), and voiceless stops became voiced. For example, Indo-European intervocalic *-t- in *teu̯teh₂ "people" resulted in Proto-Celtic *toutā, Primitive Irish *tōθā, Old Irish túath /t̪ʰuaθ/ and ultimately debuccalisation in most Irish and some Scottish dialects to /t̪ʰuəh/, shift in Central Southern Irish to /t̪ʰuəx/, and complete deletion in some Modern Irish and most Modern Scots Gaelic dialects, thus /t̪ʰuə/.[1]

An example of historical lenition in the Germanic languages is evidenced by Latin-English cognates such as pater, tenuis, cornu vs. father, thin, horn. The Latin words preserved the original stops, which became fricatives in old Germanic by Grimm's law. A few centuries later, the High German consonant shift led to a second series of lenitions in Old High German, chiefly of post-vocalic stops, as evidenced in the English-German cognates ripe, water, make vs. reif, Wasser, machen.

Although actually a much more profound change encompassing syllable restructuring, simplification of geminate consonants as in the passage from Latin to Spanish such as cuppa > /ˈkopa/ 'cup' is often viewed as a type of lenition (compare geminate-preserving Italian /ˈkɔppa/).

All varieties of Sardinian, with the sole exception of Nuorese, offer an example of sandhi in which the rule of intervocalic lenition applying to the voiced series /b d g/ extends across word boundaries. Since it is a fully active synchronic rule, lenition is not normally indicated in the standard orthographies.[2]

A series of synchronic lenitions involving opening, or loss of occlusion, rather than voicing is found for post-vocalic /p t k/ in many Tuscan dialects of Central Italy. Stereotypical Florentine, for example, has the /k/ of /kasa/ as [ˈkaːsa] casa 'house' in a post-pause realization, [iŋˈkaːsa] in casa 'in (the) house' post-consonant, but [laˈhaːsa] la casa 'the house' intervocalically. Word-internally, the normal realization is also [h]: /ˈbuko/ buco 'hole' → [ˈbuːho].

In the Celtic languages, the phenomenon of intervocalic lenition historically extended across word boundaries. This explains the rise of grammaticalised initial consonant mutations in modern Celtic languages through the loss of endings. A Scottish Gaelic example would be the lack of lenition in am fear /əm fɛr/ ("the man") and lenition in a’ bhean /ə vɛn/ ("the woman"). The following examples show the development of a phrase consisting of a definite article plus a masculine noun (taking the ending -os) compared with a feminine noun taking the ending -a. The historic development of lenition in those two cases can be reconstructed as follows:

Proto-Celtic *(s)indos wiros IPA: [wiɾos] → Old Irish ind fer [fʲeɾ] → Middle Irish in fer [fʲeɾ] → Classical Gaelic an fear [fʲeɾ] → Modern Gaelic am fear [fɛɾ]

Proto-Celtic *(s)indā benā IPA: [vʲenaː] → Old Irish ind ben [vʲen] → Middle Irish in ben [vʲen] → Classical Gaelic an bhean [vʲen] → Modern Gaelic a' bhean [vɛn]

Synchronic lenition in Scottish Gaelic affects almost all consonants (except /l̪ˠ/, which has lost its lenited counterpart in most areas).[3] Changes such as /n̪ˠ/ to /n/ involve the loss of secondary articulation; in addition, /rˠ/ → /ɾ/ involves the reduction of a trill to a tap. The spirantization of Gaelic nasal /m/ to /v/ is unusual among forms of lenition, but it is triggered by the same environment as more prototypical lenition. (It may also leave a residue of nasalization in adjacent vowels.)[4] The orthography shows that by inserting an h (except after l n r).

Some languages which have lenition have in addition complex rules affecting situations where lenition might be expected to occur but does not, often those involving homorganic consonants. This is colloquially known as 'blocked lenition', or more technically as 'homorganic inhibition' or 'homorganic blocking'. In Scottish Gaelic, for example, there are three homorganic groups:[5]

• d n t l s (usually called the dental group in spite of the non-dental nature of the palatals)
• c g (usually called the velar group)
• b f m p (usually called the labial group)

In a position where lenition is expected due to the grammatical environment, lenition tends to be blocked if there are two adjacent homorganic consonants across the word boundary. For example:[5]

• aon 'one' (which causes lenition) → aon chas 'one leg' vs aon taigh 'one house' (not aon *thaigh)
• air an 'on the' (which causes lenition) → air a' chas mhòr 'on the big leg' vs air an taigh donn "on the brown house" (not air an *thaigh *dhonn)

In modern Scottish Gaelic this rule is only productive in the case of dentals but not the other two groups for the vast majority of speakers. It also does not affect all environments any more. For example, while aon still invokes the rules of blocked lenition, a noun followed by an adjective generally no longer does so. Hence:[5]

• ad "hat" (a feminine noun causing lenition) → ad dhonn "a brown hat" (although some highly conservative speakers retain ad donn)
• caileag "girl" (a feminine noun causing lenition) → caileag ghlic "a smart girl" (not caileag *glic)

There is a significant number of frozen forms involving the other two groups (labials and velars) and environments as well, especially in surnames and place names:[5]

• MacGumaraid 'Montgomery' (mac + Gumaraid) vs MacDhòmhnaill 'MacDonald (mac + Dòmhnall)
• Caimbeul 'Campbell' (cam 'crooked' + beul 'mouth') vs Camshron 'Cameron' (cam + sròn 'nose')
• sgian-dubh 'Sgian-dubh' (sgian 'knife' + dubh '1 black 2 hidden'; sgian as a feminine noun today would normally cause lenition on a following adjective) vs sgian dhubh "a black knife" (i.e., a common knife which just happens to be black)

Though rare, in some instances the rules of blocked lenition can be invoked by lost historical consonants, for example, in the case of the past-tense copula bu, which in Common Celtic had a final -t. In terms of blocked lenition, it continues to behave as a dental-final particle invoking blocked lenition rules:[5]

• bu dona am biadh "bad was the food" versus bu mhòr am beud 'great was the pity

In Brythonic languages, only fossilized vestiges of lenition blocking occur, for example in Welsh nos da 'good night' lenition is blocked[6] (nos as a feminine noun normally causes lenition of a following modifier, for example Gwener 'Friday' yields nos Wener 'Friday night'). Within Celtic, blocked lenition phenomena also occur in Irish (for example aon doras 'one door', an chéad duine 'the first person') and Manx (for example un dorrys 'one door', yn chied dooinney 'the first man') however.

Outside Celtic, in Spanish orthographic b d g are retained as [b, d, ɡ] following nasals rather than their normal lenited forms [β, ð, ɣ].

• Crowley, Terry (1997). An Introduction to Historical Linguistics. 3rd edition. Oxford University Press.
• Oftedal, Magne (1985). Lenition in Celtic and in Insular Spanish: The Secondary Voicing of Stops in Gran Canaria. Oxford University Press, USA. ISBN 8200072827.