Consonant mutation is change in a consonant in a word according to its morphological or syntactic environment. Mutation occurs in languages around the world. A prototypical example of consonant mutation is the initial consonant mutation of all modern Celtic languages. Initial consonant mutation is also found in Indonesian or Malay, in Nivkh, in Southern Paiute and in several West African languages such as Fula. The Nilotic language Dholuo, spoken in Kenya, shows mutation of stem-final consonants, as does English to a small extent. Mutation of initial, medial and final consonants is found in Modern Hebrew. Also, Japanese exhibits word medial consonant mutation involving voicing, rendaku, in many compounds. Uralic languages like Finnish show consonant gradation, a type of consonant mutation. Similar sound changes Initial consonant mutation must not be confused with sandhi, which can refer to word-initial alternations triggered by their phonological environment, unlike mutations, which are triggered by their morphosyntactic environment. Some examples of word-initial sandhi are listed below. Spanish: , occurring after nasals and pause, alternate with , occurring after vowels and liquid consonants. Example: un [b]arco 'a boat', mi [β]arco 'my boat'. This also occurs in Hebrew (as begedkefet, an acronym for the consonants this affects), Aramaic, and Tamil. Scottish Gaelic: in some dialects, stops in stressed syllables are voiced after nasals, e.g. cat 'a cat', an cat 'the cat'. Sandhi effects like these (or other phonological processes) are usually the historical origin of morphosyntactically triggered mutation. For example, English fricative mutation (specifically, voicing) in words such as house [haus], plural houses [hauzɪz] and house (verb) [hauz] originates in an allophonic alternation of Old English, where a voiced fricative occurred between vowels (or before voiced consonants), and a voiceless one occurred initially or finally, and also when adjacent to voiceless consonants. Old English infinitives ended in -(i)an and plural nouns (of Class One nouns) ended in -as. Thus, hūs 'a house' had , and hūsian 'house (verb)' had ; however, the plural of hūs was hūs, being a neuter noun of the strong a-stem class. During the Middle English period, hous~hus, as part of the loss of gender and erosion of endings, developed plural variation, retaining hous [hu:s], the dative plural housen [hu:zən], which became extended to a general plural, and over time taking on the es plural from Old English Class 1 nouns, thus houses [hu:zəz]. After most endings were lost in English, and the contrast