In linguistics, dissimilation is a phenomenon where two sounds in a given word or phrase become less similar to each other over time. This can apply to sounds that were originally identical, or sounds that were originally similar. In general, dissimilation refers to a process of two things becoming increasingly dissimilar.
Dissimilation in language happens for a variety of reasons. In some cases, the dissimilation happens when a word makes its way from one language to another. Academics who study this sort of lexical shift may, for example, explore the migration of French words into the English lexicon. One popular example for describing this process is where various words in English, such as marble, take on an “l” sound, where, for instance, the original French word was marbre.
Other kinds of dissimilation happen with vowel sounds. Vowel sounds in languages are often known to change over time. This can happen due to the emergence of different dialects or simply to trends in common usage.
Some researchers have pinpointed specific types of dissimilating changes within a language or cultural group that uses that language. Some forms of this kind of process are known as Low Vowel Dissimilation, or LVD. When a research group considers how vowel sounds have changed over time, getting information may require working in the field, among the language communities being studied, in order to collect instances of natural dialect.
Other forms of this lexical phenomenon happen for the purposes of contrast. A language community may develop different sounds as a way to make certain words stand out in the language. In other cases, dissimulation is part of an artistic or poetic process, for example, to deal with the repetition of vowel or consonant sounds in repeating lines of song or speech.
Studying the process of dissimilation is a good example of a technical approach to language. In more utilitarian studies of language, the minor shifts of sounds usually don't have much effect on the semiotics or shared meaning that a language community relies on to use a common language. It's mainly in the study of actual phonetic influence on holistic language use that dissimilation becomes relevant and is the subject of further study; here, scholars and researchers can try to pinpoint how and why a sound has changes within a language.