Consonant mutation

Consonant mutation is a feature in languages when the sound of a consonant changes depending on morphology and syntax.
English.
In English, the plural morpheme "-(e)s" and the singular third-person present tense morpheme "-(e)s" all have different pronunciations depending on which depending on which type of phoneme, or unique sound, comes before it. These variations of the plural morpheme are called allomorphs.
In English, the past tense morpheme "-(e)d" also has different pronunciations depending on which depending on which type of phoneme comes before it.