lenition

Etymology

Analyzable as lenis + -ition, or as if from Latin lēnīt(us) + -ion, or Latin lēnītiō (“softening”) from lēniō (“soften”) + -tiō (action noun suffix) (attested since at least the 1500s, the same timeframe lenition is first attested in English with the sense "assuaging"). Modelled on German Lenierung.

noun

1. (phonetics, phonology) A weakening of articulation causing a consonant to become lenis (soft).
   Coordinate term: assimilation
   One of these processes, the process of T-Lenition, is extremely common, even though it takes place only when the input consonant is adjacent to a small number of affixes. In this change, a stopped consonant, [p t k b d g], becomes a fricative, [s, z, š, ž]. This process is called lenition, or weakening. 2001, Robert Stockwell, Donka Minkova, English Words: History and Structure, page 104
   Environments are an essential part of any discussion of lenition. Textbooks often describe lenition as occurring in the weak intervocalic or word-final environments. The canonical examples of lenition given earlier in (1) through (3) all occur either between vowels or between sonorants. 2001, Lisa M. Lavoie, Consonant Strength: Phonological Patterns and Phonetic Manifestations, page 7
   2008, Krzysztof Jaskula, Celtic, Joaquim Brandão de Carvalho, Tobias Scheer, Philippe Ségéral (editors), Lenition and Fortition, Studies in Generative Grammar: 99, page 347, As for Goidelic languages, the situation is clearer because Lenition III in this subfamily consisted in losing the same property as the first two lenitions, namely stopness.
   2011, Naomi Gurevich, 66: Lenition, Marc van Oostendorp, Colin J. Ewen, Elizabeth V. Hume, Keren Rice (editors), The Blackwell Companion to Phonology, Volume III: Phonological Processes, page 1573, Five general patterns of lenitions – all based to some extent on empirical data – are identified.