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. If the preceding sound is a sibilant consonant (one of ), or an affricate (one of ), the plural marker takes the form . Examples: mass , plural masses fez , plural fezzes mesh , plural meshes mirage , plural mirages church , plural churches bridge , plural bridges Otherwise, if the preceding sound is voiceless, the plural marker takes the likewise voiceless form . Examples: mop , plural mops mat , plural mats pack , plural packs cough , plural coughs myth , plural myths Otherwise, the preceding sound is voiced, and the plural marker takes the likewise voiced form . dog , plural dogs glove , plural gloves ram , plural rams doll , plural dolls toe , plural toes Alternation related to meaning Morphologically conditioned alternation 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: masculine petit , feminine petite "small" masculine grand , feminine grande "tall" masculine gros , feminine grosse "big" masculine joyeux , feminine joyeuse "merry" masculine franc , feminine franche "sincere" masculine bon , feminine bonne "good" Syntactically conditioned alternation 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: unmutated mór "big", mutated in bean mhór "a big woman" In Welsh, a noun undergoes soft mutation when it is the direct object of a finite verb: unmutated beic "bike", mutated in Prynodd y ddynes feic "The woman bought a bike"