In phonology, particularly within historical linguistics, dissimilation is a phenomenon whereby similar consonants or vowels in a word become less similar. For example, when a /r/ sound occurs before another in the middle of a word in rhotic dialects of English, the first tends to drop out, as in "beserk" for berserk, "supprise" for surprise, "paticular" for particular, and "govenor" for governor – this does not affect the pronunciation of government, which has only one /r/, but English government tends to be pronounced "goverment", dropping out the first n.