Regressive assimilation

In phonology, assimilation is a common phonological process by which one sound becomes more like a nearby sound. This can occur either within a word or between words. It occurs in normal speech, and it becomes more common in more rapid speech. In rapid speech, for example, "handbag" is often pronounced /ˈhæmbæɡ/. The pronunciations /ˈhænˌbæɡ/ or /ˈhændˌbæɡ/ are however common in normal speech whereas the word "cupboard", for example, is always pronounced /ˈkʌbərd/, never /ˈkʌpˌbɔrd/, and even in slow, highly articulated speech.

As in these examples, sound segments typically assimilate to a following sound (this is called regressive or anticipatory assimilation), but they may also assimilate to a preceding one (progressive assimilation). While assimilation most commonly occurs between immediately adjacent sounds, it may occur between sounds separated by others ("assimilation at a distance").

Assimilation can be synchronic—that is, an active process in a language at a given point in time—or diachronic—that is, a historical sound change.

A related process is coarticulation, where one segment influences another to produce an allophonic variation, such as vowels acquiring the feature nasal before nasal consonants when the velum opens prematurely or /b/ becoming labialised as in "boot". This article describes both processes under the term assimilation.

The physiological or psychological mechanisms of coarticulation are unknown; coarticulation is often loosely referred to as a segment being "triggered" by an assimilatory change in another segment. In assimilation, the phonological patterning of the language, discourse styles and accent are some of the factors contributing to changes observed.

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