Lenition

The opposite of lenition, fortition, a sound change that makes a consonant "stronger", is less common.

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.

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.

The phenomenon of consonant gradation in Finnic languages is also a form of lenition.

Fortition is the opposite of lenition: a consonant mutation in which a consonant changes from one considered weak to one considered strong. Fortition is less frequent than lenition in the languages of the world, but word-initial and word-final fortition is fairly frequent.