lenition

[ li-nish-uh n ]
/ lɪˈnɪʃ ən /

noun

Phonetics. a phonological process that weakens consonant articulation at the ends of syllables or between vowels, causing the consonant to become voiced, spirantized, or deleted.
Linguistics. a type of Celtic mutation that derives historically from phonological lenition.

Origin of lenition

1535–45 for obsolete sense “mitigation, assuaging”; 1910–15 for current senses; < Latin lēnīt(us) (past participle of lēnīre to soften; see lenis, -ite2) + -ion