Debuccalization or deoralization is a sound change or alternation in which an oral consonant loses its original place of articulation and moves it to the glottis (usually , , or ). The pronunciation of a consonant as [h] is sometimes called aspiration but in phonetics, aspiration is the burst of air accompanying a stop. The word comes from Latin bucca, meaning "cheek" or "mouth".
Debuccalization is usually seen as a sub-type of lenition, often defined as a consonant mutation involving the weakening of a consonant by progressive shifts in pronunciation. As with other forms of lenition, debuccalization may be synchronic or diachronic (i.e., it may involve alternations within a language depending on context or sound changes across time).
Debuccalization processes occur in many different types of environments such as the following:
/q/ is debuccalized to /?/ in several Arabic varieties, such as northern Egyptian, Lebanese, western Syrian, and urban Palestinian dialects, partially also in Jordanian Arabic (especially by female speakers). The Maltese language, which was originally an Arabic dialect, also shows this feature.
Most English-speakers in England and many speakers of American English debuccalize /t/ to a glottal stop [?] in two environments: in word-final position before another consonant (American English IPA)
In German, voiceless stops are commonly debuccalized before syllabic nasals in the following clusters: /mpm?, ltn?, ntn?, ?k/, which thus become [m?m?, l?n?, n?n?, ?]. For example, Lumpen ("rags, tatters") is pronounced [l?m?m?]. In some dialects, debuccalization may also occur before syllabic [l?], though this is less common.
Voiced stops are not usually debuccalized. However, many Upper German and East Central German dialects merge voiced and unvoiced stops at least word-internally and these merged consonants will be debuccalized. Thus in Bavarian, Anten ("ducks") and Anden ("Andes") are both pronounced ['?n?n?]. Speakers are often unaware of this.
Before a liquid or nasal, an /h/ was assimilated to the preceding vowel in Attic-Ionic and Doric and to the following nasal in Aeolic. The process is also described as loss of /h/ and subsequent lengthening of a vowel or consonant to keep the syllable the same length (compensatory lengthening).
In many varieties of Galician as well as in Galician-influenced Spanish, the phoneme /g/ may debuccalize (gheada) to in most or all instances, though and are also possible realizations. There is also an inverse hypercorrection process of older or less educated Galician speakers replacing the phoneme of the Spanish language by [g], what is called gueada.
All over Brazil, the phoneme /?/ (historically an alveolar trill /r/ that moved to an uvular position) has a rather long inventory of allophones: [r ç x ? ? ? ? ? h ?]. Only is uncommon. Few dialects, such as sulista and fluminense, give preference to voiced allophones; elsewhere, they are common only as coda, before voiced consonants.
In such dialects, especially among people speaking an educated variety of Portuguese, it is usual for the rhotic coda in the syllable rhyme to be an alveolar tap, as in European Portuguese and many registers of Spanish, or to be realized as or . In the rest of the country, it is generally realized as , even among speakers not normally using this allophone or deleting it entirely, as is common in the vernacular.
However, in some mineiro- and mineiro-influenced fluminense rural registers, [h] is used but as an allophone of (rhotic consonants are most often deleted), a mar-mal merger, instead of the much more common and less stigmatized mau-mal merger characteristic of all Brazilian urban centers except for those bordering Mercosur countries, where coda was preserved, and the entire North and Northeast regions. Its origin is the replacement of indigenous languages and línguas gerais by Portuguese, which created , and r-colored vowel as allophones of both /?/ (now mostly /?/) and /l/ (now mostly [u? ~ ]) phonemes in the coda since Natives could not easily pronounce them (caipira dialect). The later Portuguese influence from other regions made those allophones become rarer in some areas, but the mar-mal merger did not disappear in a few isolated villages and towns.
Finally, many fluminense registers, especially those of the poor and of the youth, most northern and northeastern dialects, and, to a much minor degree, all other Brazilian dialects, debuccalize /s/ (that is, [? ~ ?]) but less so than in Spanish. However, a mar-mas merger or even a mar-mais merger occurs: mas mesmo assim "but even so" or mas mesma, sim "though, right, the same (f) one" [m 'me?m? 's?]; mais light "lighter, more slim", or also "less caloric/fatty" ['ma? 'lajt?]; mas de mim, não "but from me, no" or mais de mim, não "not more from me" ['ma? d?i 'm? 'nw]. A coda rhotic in the Brazilian dialects in the Centro-Sul area is hardly ever glottal, and the debuccalized /s/ is unlikely to be confused with it.
Debuccalization can be a feature of loanword phonology. For example, while Korean allows certain coda obstruents, Japanese does not. Those consonants realized in Korean as unreleased voiceless stops ([p? t? k?]) may be realized in Japanese as glottal stops: