Alternation (linguistics)

In linguistics, an alternation is the phenomenon of a morpheme exhibiting variation in its phonological realization. Each of the various realizations is called an alternant. The variation may be conditioned by the phonological, morphological, and/or syntactic environment in which the morpheme finds itself.

Alternations provide linguists with data that allow them to determine the allophones and allomorphs of a language's phonemes and morphemes and to develop analyses determining the distribution of those allophones and allomorphs.

An example of a phonologically conditioned alternation is the English plural marker commonly spelled s or es.[1] This morpheme is pronounced /s/, /z/, or /ᵻz/,[note 1] depending on the nature of the preceding sound.

French has an example of morphologically conditioned alternation. The feminine form of many adjectives ends in a consonant sound that is missing in the masculine form. In spelling, the feminine ends in a silent e, while the masculine ends in a silent consonant letter:[2]

Syntactically conditioned alternations can be found in the Insular Celtic languages, where words undergo various initial consonant mutations depending on their syntactic position.[3] For example, in Irish, an adjective undergoes lenition after a feminine singular noun:

In Welsh, a noun undergoes soft mutation when it is the direct object of a finite verb: