Definition of lenition in US English:

lenition

noun

  • The process or result of weakened articulation of a consonant, causing the consonant to become voiced, spirantized, or lost.

    • ‘The grammar involved in medieval Gaelic names often includes lenition, a "softening" of the initial consonant sound of words or names required by Gaelic grammar in certain situations.’

Origin

Early 20th century: from Latin lenis ‘soft’ + -ition, suggested by German Lenierung.

Pronunciation

lenition

/ləˈniSH(ə)n/