Assimilation is a process of alteration of speech sounds as a result of which one of the sounds becomes fully/partially similar to the adjoining sound.
Types of assimilation:
according to direction: progressive, regressive, reciprocal.
according degree of completeness: complete (two adjoining sounds become alike/merge into one), incomplete(assimilated sound retains its major articulatory features).
according degree of stability: obligatory (historical), non-obligatory
According to the change of theplace of obstruction [t, d, n, l] + [θ,ð] – alveolar sounds become dental when followed by interdental sounds. [t, d, n, l, s, z] + [r] – become post-alveolar, [m, p] + [f,v] – bilabial sounds become labio-dental.
According to the change of the work of vocal cords. Sonorants [m, n, l, r, j, w] are partially devoiced when preceded by voiceless cons. The suffixes –s depend on the quality of the preceding cons. The pronunciation of the –ed flexion depends on the last sound of the stem.
According to the change of the lip position. Consonants followed by [w] become lip-rounded.
According to the change of the position of the soft palate nasal cononants [m, n] influence preceding [t,d].
According to the change of the manner of release of plosive consonants: [p, b, t, d, g, k] + [n, m] – nasal plosion e.g.button, [p, b, t, d, g, k] + [l] – lateral plosion e,g, bottle, [p, b, t, d, g, k] + [p, b, t, d, g, k, tS, dj] – loss of plosion. Loss of aspiration [s] + [p, t, k].