|Sound change and alternation|
Mutation phenomena occur 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 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. Japanese exhibits word medial consonant mutation involving voicing, rendaku, in many compounds.
Celtic languages 
The Celtic languages are well known for their initial consonant mutations. The individual languages vary on the number of mutations available: the Goidelic languages — Scottish Gaelic, Manx and Irish — have two, Welsh and Cornish (both Brythonic languages) each have three (but not the same three) and Breton (also a Brythonic language) has four. Additionally, Irish and the Brythonic languages have so-called "mixed mutations", where a trigger causes one mutation to some sounds and another to other sounds. The languages vary on the environments for the mutations, though some generalizations can be made. In all the languages, feminine singular nouns are mutated after the definite article, and adjectives are mutated after feminine singular nouns. In most of the languages, the possessive adjectives trigger various mutations. Following are some examples from Breton, Irish, and Welsh:
|ar wreg vras||an bhean mhór||y wraig fawr||the big woman|
|e gazh||a chat||ei gath||his cat|
|he c'hazh||a cat||ei chath||her cat|
|o c'hazh||a gcat||eu cath||their cat|
Older textbooks on Gaelic sometimes refer to the c → ch mutation as "aspiration", but it is not aspiration in the sense of the word used by modern phoneticians, and linguists prefer to speak of lenition here.
Historically, the Celtic initial mutations originated from progressive assimilation and sandhi phenomena between adjacent words. For example, the mutating effect of the conjunction a 'and' is due to the fact that it used to have the form *ak, and the final consonant influenced the following sounds.
For details see the articles on the individual languages:
- Breton mutations
- Cornish language: grammar
- Irish initial mutations
- Manx language: initial consonant mutations
- Scottish Gaelic: Lenition
- Welsh morphology
Another type of consonant mutation found in the Celtic languages is affection.
Central Vanuatu languages 
For example, in Raga language:
- nan vano "I went"
- nam bano "I go"
These patterns of mutations probably arose when a nasal prefix, used to indicate realis mood, became combined with the initial consonant of the verb. The possible ancestral pattern of mutation, and its descendants in some modern Central Vanuatu languages, are shown below:
|Proto-Central Vanuatu||*k > *ŋk||*r > *nr||*p > *mp|
|Raga (Pentecost)||x > ŋg||t > d||v / vw > b / bw|
|northern Apma (Pentecost)||k > ŋg||t > d||v / w > b / bw|
|southern Apma (Pentecost)||v / w > b / bw|
|Ske (Pentecost)||z > d||v / vw > b / bw|
|Lonwolwol (Ambrym)||r > rV||∅ > bV|
|Southeast Ambrym||x / h / ∅ > g||t > d||v / h > b|
|northern Paama||∅ > k||t > r|
|central/southern Paama||k / ∅ > g / ŋ||t / r > d|
|Nāti (Malekula)||k / ʔ > ŋk||t / r > nt / ntr||v / w > mp / mpw|
|Maii (Epi)||t > d||v > b|
|Lewo (Epi)||v / w > p / pw|
|Lamenu (Epi)||∅ > p|
|Bierebo (Epi)||k > ŋk||t / c > nd / nj||v / w > p / pw|
|Baki (Epi)||c > s||v > mb|
|Bieria (Epi)||t > nd||v > mb|
|Nakanamanga (Efaté-Shepherds)||k > ŋ||r > t||v / w > p / pw|
|Namakir (Shepherds)||k > ŋ||t / r > d||v / w > b|
The Dholuo language (one of the Luo languages) shows alternations between voiced and voiceless states of the final consonant of a noun stem. In the construct state (the form that means 'hill of', 'stick of', etc.) the voicing of the final consonant is switched from the absolute state. (There are also often vowel alternations that are independent of consonant mutation.)
- ɡɔt 'hill' (abs.), god (const.)
- lʊθ 'stick' (abs.), luð (const.)
- kɪdo 'appearance' (abs.), kit (const.)
- tʃoɡo 'bone' (abs.), tʃok (const.)
- buk 'book' (abs.), bug (const.)
- kɪtabu 'book' (abs.), kɪtap (const.)
Consonant alternation related to palatalization is frequent in English vocabulary of Latinate origin. One subtype affects the sibilant consonants: earlier *sj *zj were palatalized, leading to an alternation between alveolar /s z/ and postalveolar /ʃ ʒ/.
- confess /kənˈfɛs/ : confession /kənˈfɛʃən/
- fuse /fjuːz/ : fusion /ˈfjuːʒən/
Another, unproductive layer results from the Vulgar Latin palatalization of velar stops before front vowels, and is thus imported from the Romance languages. Here /k g/ alternate with /s d͡ʒ/.
- induce /ɪnˈdjuːs/ : induction /inˈdʌkʃən/
- magic /ˈmæd͡ʒɪk/ : magus /meɪgəs/
A combination of inherited and loaned alternation also occurs: an alternation pattern *t : *sj was brought over in Latinate loanwords, which in English was then turned into an alternation between /t/ and /ʃ/.
- act /ækt/ : action /ˈækʃən/
English has had its own palatalization of velar stops as well during the Old English period. While most original alternations resulting from this have been levelled, traces occur in some word doublets such as ditch /dɪt͡ʃ/ ~ dike /daɪk/.
In the past tense of certain verbs, English also retains traces of several ancient sound developments such as *kt > *xt and ŋx > *x; many of these have been further complicated following the loss of *x in the Middle English period.
- seek /siːk/ : sought /sɔːt/
- think /θɪŋk/ : thought /θɔːt/
An example showing the effects of both this and palatalization is catch /kæt͡ʃ/ : caught /kɔːt/.
Consonant mutation is a prominent feature of the Fula language. The Gombe dialect spoken in Nigeria, for example, shows mutation triggered by declension class. The mutation grades are fortition and prenasalization:
|j||dʒ, ɡ||ɲdʒ, ŋɡ|
For example, the stems rim- 'free man' and [ɣim-] 'person' have the following forms:
- [rimɓe] (class 2), dimo (class 1), ndimon (class 6)
- [ɣimɓe] (class 2), gimɗo (class 1), ŋgimkon (class 6)
For example, some verbs show mutation between tenses and conjugation classes:
- [katav] "he wrote", [jixtov] "he will write"
- [hitbia] "he sank" (transitive), [tava] "he sank" (intransitive)
Some nouns show mutation between masculine and feminine, between singular and plural, or after prepositions:
- [melex] "a king", [malka] "a queen", [melaxim] "kings", [melaxot] (spoken Hebrew, [malkot])
- [dov] "a bear" (masc.), [duba] "a bear" (fem.), [dubim] "bears" (masc.), [dubot] "bears" (fem.)
- [bajit] "a house", [be-vajit] "in a house" (in spoken Modern Hebrew: [be-bajit]
But some words do not have alternations:
- [xatav] "he hacked", [jaxtov] "he will hack"
- [tov] "good", [tovin]~[tovim] "goods"
- [kibut͡s] "a kibbutz", [be-kibut͡s] "in a kibbutz"
In some limited cases, initial mutation can signal adverbial status in spoken Modern Hebrew:
- [bakaʃa] "a request", [be-vakaʃa] "please" (spoken or written, "בבקשה"), [vakʃa] "please" (spoken, informal).
Indonesian and Malay 
The active form of a multisyllabic verb with an initial stop consonant or fricative consonant is formed by prefixing the verb stem with meN-, in which N stands for a nasal sharing the place of articulation as the initial consonant.
- garuk → menggaruk (= to scratch), hitung → menghitung (= to count),
- beri → memberi (= to give), fitnah → memfitnah (= to accuse falsely),
- cari → mencari (= to search), dapat → mendapat (= to obtain), *jangkau → menjangkau (= to reach)
If the initial consonant is an unvoiced stop or s, it disappears, leaving only the nasal in its place.
- kandung → mengandung (= to contain or to be pregnant),
- putih → memutih (= to turn white),
- satu → menyatu (= to become one / to unite),
- tulis → menulis (= to write).
Applied to verbs starting with a vowel, the nasal is realized as ng ([ŋ]).
Monosyllabic verbs add an epenthetic vowel before prefixing, producing the prefix menge-.
- bor (= boring tool / drill) → mengebor (= to make a hole with drill).
Rendaku (meaning sequential voicing) is a mutation of the initial consonant of a non-initial component in a Japanese compound word. Some compounds exhibiting rendaku:
nigiri + sushi → nigirizushi ("grip (with the hand)" + "sushi" → "hand-shaped sushi")
nigori + sake → nigorizake ("muddy" + "rice wine" → "unfiltered sake")
Nigori in "nigorizake" and the daku in "rendaku" are actually different readings (see On-yomi and Kun-yomi) of the same kanji 濁, because voiced and unvoiced consonants are described in Japanese as opaque and clear.
The most common classes of mutations involve
- velar/postalveolar alternation /k/→/tɕ/ (к→ч), /ɡ/→/ʐ/ (г→ж), /x/→/ʂ/ (х→ш): тихий/тише (comparative adjective: quiet→quieter)
- Gain/loss of palatalization: царь/царский (adjective formation: tsar (n.)/ tsar (adj.))
Other common mutations are:
- /t/→/tɕ/ (т→ч), /d/→/ʐ/ (д→ж)
- /z/→/ʐ/ (з→ж), /s/→/ʂ/ (с→ш), /ts/→/tɕ/ (ц→ч)
- /sk/→/ɕː/ (ск→щ): плеск → плещет "splash" / "(he) splashes", /st/→/ɕː/ (ст→щ): свистеть → свищу "to whistle" / "I whistle"
Uralic languages 
Ute language 
In the Ute language, also called Southern Paiute, there are three consonant mutations, which are triggered by different word-stems. The mutations are Spirantization, Gemination, and Prenasalization:
For example, the absolutive suffix -pi appears in different forms, according to which noun stem it is suffixed to:
- movi-ppi 'nose'
- sappI-vi 'belly'
- aŋo-mpi 'tongue'
Artificial languages 
The Sindarin language created by J. R. R. Tolkien has mutation patterns inspired by those of Welsh. The first letter of a noun usually undergoes mutation when the noun follows a closely associated word such as an article or preposition. Thus, we get certh, rune, and i gerth, the rune. Also, second elements of compounds and direct objects of verbs undergo mutation.
The philosophical Ithkuil language features a complex mutation pattern, with every root consonant having eight possible mutations of its base form. Idiosyncratically, these are all consonant clusters rather than single consonants. Its phonologically simpler successor Ilaksh retains the feature as well, though reduces the grades to three.
Mutation vs. sandhi 
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: [b, d, ɡ], occurring after nasals and pause, alternate with [β, ð, ɣ], occurring after vowels and liquid consonants. Example: un [b]arco 'a boat', mi [β]arco 'my boat'. This also occurs in Hebrew, Aramaic and Tamil.
- Scottish Gaelic: in some dialects, stops in stressed syllables are voiced after nasals, e.g. [kʰaht] 'a cat', [əŋ ɡaht] 'the cat'.
Sandhi effects like these (or other phonological processes) are usually the historical origin of morphosyntactically triggered mutation. For example, the English fricative mutation described above originates in an allophonic alternation of Old English, where a voiced fricative occurred between vowels (or other 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 one very common declension class) ended in -as. Thus, hūs 'a house' had [s], while hūsas 'houses' and hūsian 'to house' had [z]. After most endings were lost in English, and the contrast between voiced and voiceless fricatives phonemicized (largely due to the influx of French loanwords), the alternation was morphologized.
Further reading 
- Zimmer, Stefan. The Celtic Mutations: some typological comparisons. A Companion in Linguistics, a Festschrift for Anders Ahlqvist, ed. B. Smelik, R. Hofman, C. Hamans, D. Cram. Nijmegen: de Keltische Draak / Münster: Nodus 2004, 127-140.
See also 
- Ball, M. J.; N. Müller (1992). Mutation in Welsh. London: Routledge. ISBN 0-415-03165-6.
- Fife, James; Gareth King (1998). "Celtic (Indo-European)". In in Andrew Spencer and Arnold M. Zwicky (eds.),. The Handbook of Morphology. Oxford: Blackwell. pp. 477–99. ISBN 0-631-22694-X.
- Ternes, Elmar. 1986. A Grammatical hierarchy of joining. In: Andersen, Henning. Sandhi phenomena in the languages of Europe. P.17-18
- Crowley T, 1991. Parallel Development and Shared Innovation: Some Developments in Central Vanuatu Inflectional Morphology. Oceanic Linguistics, Vol. 30, No. 2, pp. 179-222
- Stafford, R. (1967). The Luo language. Nairobi: Longmans.
- Arnott, D. W. (1970). The Nominal and Verbal Systems of Fula. Oxford: Oxford University Press.
- Glinert, Lewis (1989). The Grammar of Modern Hebrew. Cambridge: Cambridge University Press.
- Examples adapted from Wikibooks:Indonesian_prefix_me
- Sapir, Edward (1930). "The Southern Paiute Language (Part I): Southern Paiute, a Shoshonean Language". Proceedings of the American Academy of Arts and Sciences 65: 1–296.