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.

Phonologically conditioned alternation

An example of a phonologically conditioned alternation is the English plural marker commonly spelled s or es. This morpheme is pronounced,, or, depending on the nature of the preceding sound.
  1. If the preceding sound is a sibilant consonant, or an affricate, the plural marker takes the form. Examples:
  2. *mass, plural masses
  3. *fez, plural fezzes
  4. *mesh, plural meshes
  5. *mirage, plural mirages
  6. *church, plural churches
  7. *bridge, plural bridges
  8. Otherwise, if the preceding sound is voiceless, the plural marker takes the likewise voiceless form. Examples:
  9. *mop, plural mops
  10. *mat, plural mats
  11. *pack, plural packs
  12. *cough, plural coughs
  13. *myth, plural myths
  14. Otherwise, the preceding sound is voiced, and the plural marker takes the likewise voiced form.
  15. *dog, plural dogs
  16. *glove, plural gloves
  17. *ram, plural rams
  18. *doll, plural dolls
  19. *toe, plural toes

    Alternation related to meaning

Morphologically conditioned alternation

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:
Syntactically conditioned alternations can be found in the Insular Celtic languages, where words undergo various initial consonant mutations depending on their syntactic position. 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: