Dahl's law (German: das Dahlsche Gesetz[1]) is a sound rule in some of the Northeast Bantu languages that illustrates a case of voicing dissimilation.
The law was named in 1903 by Carl Meinhof in his paper "Das Dahlsche Gesetz": in the paper, Meinhof explains that he named the rule after his pupil, the Moravian missionary Edmund Dahl, who reported it in 1897 when visiting the Wanyamwezi tribe in Urambo.
In other languages the law is no longer productive, but there are indications that it once was (such as in Taita, Kamba/Daisũ, Taveta and Luhya/Logooli).
In some neighboring languages (and in other dialects of Nyamwezi) words reflecting Dahl's law are found, but they appear to be transfers from languages in which the law is productive.
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