The tendency for the articulation of speech sounds to adjust to that of sounds in their environment. A simple example is the spread of lip rounding to a preceding or following sound. Thus the first consonant in the English word twin has lip rounding because of the lip rounding of the following w. Compare the first consonant in tin. Almost any feature of articulation may spread in this way. Other examples are nasality spreading from a nasal stop to an adjacent sonorant, minor adjustments in the place of articulation conditioned by the place of articulation of a neighbouring sound, and the devoicing of consonants caused by voicelessness in the the immediate environment. Coarticulation may be anticipatory: a sound is influenced by a following sound, or perseverative: an earlier sound influences one which follows.

See also assimilation.