Dissimilation

Dissimilation is a phonological process.  In assimilation sounds become more similar to one another.  In dissimilation, however, the reverse occurs- sounds become less similar from one another. 

In Kurundi, an African language spoken in Burundi, a consonant in the prefix must disagree in voicing with a the first consonant of the root to which it is attached.  The rule can be states as follows:

A voiced root initial segment requires a voiceless consonant in the prefix and a voiceless root initial segment requires a voiced consonant in the prefix.  The data illustrates this:

Imperative

rya eat

1st person singular present

tu-rya

Imperative

mwa shave

1st person singular present

tu-mwa

Imperative

soma read

1st person singular present

du-soma

Imperative

kubita hit

1st person singular present

du-kubita

The prefix variant du occurs with roots that have a voiceless initial segment in the root.  With roots that have a voiced initial segment in the root, the prefix variant tu occurs.  The examples from Kurundi serve to illustrate the phonological process of dissimilation.