Lenition and Fortition

The sound changes known as lenition and fortition depend on a hierarchy of consonant strength. Such a strength hierarchy can be considered as the converse of the sonority hierarchy, that is, sounds that are high in sonority are low in strength and vice versa. Sonority is described elsewhere in this encyclopedia but may be thought of as the degree of sound clarity derived from the degree of opening of the vocal tract (the more open the more sonorous). The strength hierarchy, on the other hand, classifies the strongest consonants as those with the greatest degree of closure and those without vocal fold vibration. Thus, plosives are stronger than fricatives, and voiceless plosives are stronger than voiced. Sound changes that involve moving from a stronger to ...