 Coarticulation refers to a situation in which a conceptually isolated speech sound is influenced by a preceding or following speech sound. There are two main types of coarticulation. The first concerns the production of a coarticulated consonant, that is a consonant with two simultaneous places of articulation. An example of such a sound is the voiceless labiovila plosif found in many West African languages. Appa. Appa. Or take the labiovila weh as in Awa. Awa. In both cases we have two primary places of articulation that are articulated together. Another variant of coarticulation is the assimilation of the place of articulation of one speech sound to that of an adjacent speech sound. For example, while the sound N in English normally involves an alveolar place of articulation as in 10, in the word 10th it is pronounced with a dental place of articulation because the following sound is dental. Or take the pronunciation of the vela plosif ke. Whenever ke precedes a front vowel as in ki, the constriction at the velum is fronted, shown by a plus sign as subscript. Whenever ke precedes a back vowel as in ku, the tongue is retracted, shown by a minus sign as subscript. Coarticulation should not be mixed up with secondary articulation, which often stretches over several segments.