DIS-
SIMI-
LATION
The process by which two similar or identical sounds in a word become less alike.
Why does this happen?
Languages are lazy. Or rather, speakers are striving for efficiency. When a word contains two identical or very similar sounds close together, it can be physically awkward to articulate them in rapid succession (a "tongue twister" effect).
To make pronunciation easier and to make the acoustic signal clearer to the listener, one of the sounds will randomly mutate or be deleted entirely. The sounds dissimilate.
1. Liquid Dissimilation (l and r)
This is the most frequent type of dissimilation in English, often inherited from Latin. English has a phonetic constraint that makes it difficult to process two l sounds or two r sounds in close proximity. The Suffix Rule: The Latin suffix -alis (pertaining to) usually remains -al in English. However, if the root word already contains an l, the suffix dissimilates to -ar.
Result: Singular
To avoid the repetitive "singul-al", the suffix dissimilates to -ar.
Result: Modular
To avoid "modul-al", the suffix dissimilates to -ar.
Result: Lunar
From Luna (Moon). To avoid "lun-al", the suffix dissimilates to -ar.
2. Rhotic Dissimilation (The 'R-Drop')
In standard and rapid English speech, if two r sounds (rhotic consonants) appear in consecutive syllables, the first one is frequently deleted or changed to a glide. This simplifies the 'tongue-bunching' required.
Result: Feb-yu-ary
The first r is often dropped (/ˈfɛbjʊɛri/) because the brain anticipates the second r at the end.
Result: Be-zerk
Commonly pronounced as "be-zerk" rather than "ber-zerk".
Result: Guv-en-er
Often pronounced "guv-en-er", dropping the internal r to avoid repetitive rhoticity.
3. Fricative Dissimilation
Fricatives (sounds made by forcing air, like f, s, th, x) are acoustically 'noisy'. When two appear together, one may switch to a 'stop' (completely blocked airflow, like t, k) to create clearer contrast.
Result: Fift
In many modern dialects, the second fricative (th) is dissimilated to a t (/fɪft/).
Result: Sikst
Similar to 'fifth', the ending fricative is frequently changed to a t to replace a 'hiss' with a 'click'.
4. Dissimilation in Loanwords
When English adopts words from French or Latin, it often 'fixes' repetitive sounds that existed in the source language to make them more distinct for English speakers.
Result: Purple
The Old French 'purpre'. English speakers found the double r redundant. The second r dissimilated into an l.
Result: Turtle
Derived from Latin 'turtur'. The repetition was broken by changing the final r to an l.
Language is always optimizing.
Dissimilation shows us that language is primarily a physical act. When our mouths stumble over repetitive sounds, the language simply adapts by making sounds less alike.