Assimilation in Speech

Assimilation is a general term in phonetics for the process by which a speech sound becomes similar or identical to a neighboring sound. In the opposite process, dissimilation, sounds become less similar to one another. The term "assimilation" comes from the Latin meaning, "make similar to."

Examples and Observations

"Assimilation is the influence of a sound on a neighboring sound so that the two become similar or the same. For example, the Latin prefix in- 'not, non-, un-' appears in English as il-, im-. and ir- in the words illegal, immoral, impossible (both m and p are bilabial consonants), and irresponsible as well as the unassimilated original form in- in indecent and incompetent. Although the assimilation of the n of in- to the following consonant in the preceding examples was inherited from Latin, English examples that would be considered native are also plentiful. In rapid speech native speakers of English tend to pronounce ten bucks as though it were written tembucks, and in anticipation of the voiceless s in son the final consonant of his in his son is not as fully voiced as the s in his daughter, where it clearly is [z]."
(Zdenek Salzmann, "Language, Culture, and Society: An Introduction to Linguistic Anthropology. Westview," 2004)

"Features of adjacent sounds may combine so that one of the sounds may not be pronounced. The nasal feature of the mn combination in hymn results in the loss of /n/ in this word (progressive assimilation), but not in hymnal. Likewise, the alveolar (upper gum ridge) production of nt in a word such as winter may result in the loss of /t/ to produce a word that sounds like winner. However, the /t/ is pronounced in wintry."
(Harold T. Edwards, "Applied Phonetics: The Sounds of American English." Cengage Learning, 2003)

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Dissimilation and Haplology in Phonetics

By Richard Nordquist

Partial Assimilation and Total Assimilation

"[Assimilation] may be partial or total. In the phrase ten bikes, for example, the normal form in colloquial speech would be /tem baiks/, not /ten baiks/, which would sound somewhat 'careful.' In this case, the assimilation has been partial: the /n/ sound has fallen under the influence of the following /b/, and has adopted its bilabiality, becoming /m/. It has not, however, adopted its plosiveness. The phrase /teb baiks/ would be likely only if one had a severe cold! The assimilation is total in ten mice /tem mais/, where the /n/ sound is now identical with the /m/ which influenced it."
(David Crystal, "Dictionary of Linguistics and Phonetics, 6th ed." Blackwell, 2008)

Alveolar Nasal Assimilation: "I Ain't No Ham Samwich"

"Many adults, especially in casual speech, and most children assimilate the place of articulation of the nasal to the following labial consonant in the word sandwich:
sandwich /sænwɪč/ → /sæmwɪč/
The alveolar nasal /n/ assimilates to the bilabial /w/ by changing the alveolar to a bilabial /m/. (The /d/ of the spelling is not present for most speakers, though it can occur in careful pronunciation.)"
(Kristin Denham and Anne Lobeck, Linguistics for Everyone. Wadsworth, 2010)

Direction of Influence

"Features of an articulation may lead into (i.e. anticipate) those of a following segment, e.g. English white pepper /waɪt 'pepə/ → /waɪp 'pepə/. We term this leading assimilation.
"Articulation features may be held over from a preceding segment, so that the articulators lag in their movements, e.g. English on the house /ɑn ðə 'haʊs/ → /ɑn nə 'haʊs/. This we term lagging assimilation.
"In many cases, there is a two-way exchange of articulation features, e.g. English raise your glass /'reɪz jɔ: 'glɑ:s/ → /'reɪʒ ʒɔ: 'glɑ:s/. This is termed reciprocal assimilation."
(Beverley Collins and Inger M. Mees, "Practical Phonetics and Phonology: A Resource Book for Students," 3rd ed. Routledge, 2013)

Elision and Assimilation

"In some situations, elision and assimilation can apply at the same time. For example, the word 'handbag' might be produced in full as /hændbæg/. However, the /d/ is in a site where elision is possible, so the phrase could be produced as /hænbæg/. Furthermore, when the /d/ is elided, it leaves /n/ in a position for place assimilation. So, we frequently hear /hæmbæg/. In this final example, we see again that connected speech processes have the potential to influence meaning. Is /hæmbæg/ a rendition of 'handbag' with elision and ​dealveolarisation, or is it simply 'ham bag'? In real life, the context and knowledge of the speaker's habitual patterns and preferences would help you to decide, and you would probably opt for the most likely meaning. So, in reality, we are rarely confused by CSPs [connected speech processes], although they do have the potential to cause misunderstandings."
(Rachael-Anne Knight, "Phonetics: A Coursebook." Cambridge University Press, 2012)