assimilation [Lat. assimilare ‘to make like (to)’]
Articulatory adaptation of one sound to a nearby sound with regard to one or more features (articulation). Assimilation has numerous aspects. (a) Assimilation can be a matter of (i) the place of articulation, e.g. the n in incomplete pronounced as [ŋ]; (ii) the manner of articulation. e.g./in/>[ir] in irregular); or (iii) the glottal state, e.g. the pronunciation of the plural morpheme {-s} in dogs and cats [kæts]. (This is also called ‘voicing assimilation.’) (b) Depending on the direction of influence in a sound sequence, a distinction is drawn between progressive (or perseverative) assimilation, in which a following sound adapts itself to a preceding one (as in vowel harmony), and regressive (or anticipatory) assimilation, in which a preceding sound takes on a feature or features of a following sound (as in umlaut). (c) A distinction is also made between complete and partial assimilation.
Complete assimilation describes the leveling of two sounds (as in irregular, above), which is always the case if the sounds are differentiated by only one feature. Partial assimilation refers to the change of only one of several features (as in incomplete, above). (d) Assimilation can also be reciprocal (also called ‘bi-directional’ or ‘fusional’), when a mutual adaptation occurs, and a third sound replaces the two original sounds: [ti]>[∫] in nation ['nei∫әn]. (e) If the process involves adjacent sounds, it is a case of contact assimilation. Otherwise it is called distant assimilation. (alsocoarticulation, labialization,monophthongization, palatalization)
References
Vennemann, T. 1972. Phonetic detail in assimilation. Problems in Germanic phonology. Lg 48. 863–92.
and cats [kæts]. (This is also called ‘voicing assimilation.’) (b) Depending on the direction of influence in a sound sequence, a distinction is drawn between progressive (or perseverative) assimilation, in which a following sound adapts itself to a preceding one (as in 
