Coarticulation in its general sense refers to a situation in which a conceptually isolated speech sound is influenced by, and becomes more like, a preceding or following speech sound. There are two types of coarticulation: anticipatory coarticulation, when a feature or characteristic of a speech sound is anticipated (assumed) during the production of a preceding speech sound; and carryover or perseverative coarticulation, when the effects of a sound are seen during the production of sound(s) that follow. Many models have been developed to account for coarticulation. They include the look-ahead, articulatory syllable, time-locked, window, coproduction and articulatory phonology models.

Coarticulation in phonetics refers to two different phenomena:

• the assimilation
  Assimilation (linguistics)
  Assimilation is a common phonological process by which the sound of the ending of one word blends into the sound of the beginning of the following word. This occurs when the parts of the mouth and vocal cords start to form the beginning sounds of the next word before the last sound has been...
  
  of the place of articulation
  Place of articulation
  In articulatory phonetics, the place of articulation of a consonant is the point of contact where an obstruction occurs in the vocal tract between an articulatory gesture, an active articulator , and a passive location...
  
   of one speech sound to that of an adjacent speech sound. For example, while the sound /n/ of English
  English language
  English is a West Germanic language that arose in the Anglo-Saxon kingdoms of England and spread into what was to become south-east Scotland under the influence of the Anglian medieval kingdom of Northumbria...
  
   normally has an alveolar
  Alveolar consonant
  Alveolar consonants are articulated with the tongue against or close to the superior alveolar ridge, which is called that because it contains the alveoli of the superior teeth...
  
   place of articulation, in the word tenth it is pronounced with a dental place of articulation because the following sound, /θ/, is dental.
• the production of a co-articulated consonant
  Co-articulated consonant
  Co-articulated consonants or complex consonants are consonants produced with two simultaneous places of articulation. They may be divided into two classes, doubly articulated consonants with two primary places of articulation of the same manner , and consonants with secondary articulation, that is,...
  
  , that is, a consonant with two simultaneous places of articulation. An example of such a sound is the voiceless labial-velar plosive
  Voiceless labial-velar plosive
  The voiceless labial–velar plosive is a type of consonantal sound, used in some spoken languages. It is a and pronounced simultaneously. To make this sound, say Coe, but close your lips as if you were saying Poe; release your lips at the same times as or a fraction of a second after you pronounce...
  
   /k͡p/ found in many West Africa
  West Africa
  West Africa or Western Africa is the westernmost region of the African continent. Geopolitically, the UN definition of Western Africa includes the following 16 countries and an area of approximately 5 million square km:-Flags of West Africa:...
  
  n languages.

The term coarticulation may also refer to the transition from one articulatory gesture

Gesture

A gesture is a form of non-verbal communication in which visible bodily actions communicate particular messages, either in place of speech or together and in parallel with spoken words. Gestures include movement of the hands, face, or other parts of the body...

to another.