coarticulation

Coarticulation is the phenomenon whereby the articulation of a speech sound overlaps with the articulation of neighboring sounds. In fluent speech, the movements of the lips, tongue, jaw, and other articulators are not isolated to single segments but are coordinated across sequences, so that, for example, preparation for a following sound begins before its turn.

There are two broad directions of coarticulation: anticipatory (regressive) coarticulation, where upcoming segments influence the current articulation; and carryover (progressive) coarticulation, where the present gesture carries over into the following segment. Both directions occur widely and vary with speaking rate, dialect, and language.

A classic illustration is that the tongue and lips begin to adjust in anticipation of a forthcoming consonant or vowel; the quality of an already produced vowel can be subtly altered by a following consonant, and the reverse can happen when the consonant begins before its release. This results in continuous changes in articulatory posture and acoustic cues such as formant transitions.

Methods to study coarticulation include electromagnetic articulography, ultrasound imaging of the tongue, MRI-based dynamic tracking, and palatography. Theoretically, coarticulation is central to articulatory phonology, which models speech as overlapping gestures rather than strictly discrete units. It helps explain why speech sounds are context-dependent and why phonetic implementations vary across rate and style.

Understanding coarticulation informs speech synthesis, recognition, language development, and clinical work on speech disorders, and remains a fundamental concept in phonetics and linguistics.