What is lenition?

Most phonological textbooks and treatises do not define lenition or weakening, as it is also called. Instead they provide a list of examples of processes which they wish to term ‘lenitions’ or ‘weakenings’. It is then hoped that the reader will deduce a correct definition. This is what is done in, for example, Lass & Anderson (1975: 150) and Sommerstein (1977: 228). One of the few available definitions of lenition is to be derived from Vennemann's definition of relative weakness (cited in Hyman, 1975: 165): ‘A segment X is said to be weaker than a segment Y if Y goes through an X stage on its way to zero.’ According to this definition, lenition is primarily a diachronic process affecting the sound structure of languages. It may also have synchronie reflexes (such as initial consonant mutations in the Celtic languages), but these are called ‘lenitions’ by an extension of the term from diachrony.