||This article needs additional citations for verification. (June 2010)|
|Sound change and alternation|
In phonetics, nasalization (or nasalisation) is the production of a sound while the velum is lowered, so that some air escapes through the nose during the production of the sound by the mouth. An archetypal nasal sound is [n].
In the International Phonetic Alphabet nasalization is indicated by printing a tilde diacritic U+0303 ◌̃ combining tilde (HTML:
̃) above the symbol for the sound to be nasalized: [ã] is the nasalized equivalent of [a], and [ṽ] is the nasalized equivalent of [v]. An older IPA subscript diacritic [ą], called an ogonek, is still seen, especially when the vowel bears tone marks that would interfere with the superscript tilde. For example, [ą̄ ą́ ą̀ ą̂ ą̌] are more legible in most fonts than [ã̄ ã́ ã̀ ã̂ ã̌].
Nasal vowels 
Nasal vowels are found in some European languages, such as French, Portuguese, Breton, and Polish. In these, as well as and languages found in other language families outside Europe, nasal vowels contrast with oral vowels. Many languages, however, only have oral vowels.
There are occasional cases where vowels show contrasting degrees of nasality.
Nasal consonants 
By far the most common nasal sounds are nasal consonants such as [m], [n] or [ŋ]. Most nasal consonants are occlusives, where airflow through the mouth is blocked and redirected through the nose. Their oral counterparts are the stops.
Other nasal(ized) consonants 
Nasalized versions of other consonant sounds also exist, though they are much rarer than either nasal occlusives or nasal vowels. Some of the South Arabic languages use phonemic nasalized fricatives, such as /z̃/, which sounds something like a simultaneous [n] and [z]. The sound written ⟨r⟩ in Mandarin has an odd history; for example, it has been borrowed into Japanese as both [z] and [n]. It seems likely that it was once a nasalized fricative, perhaps a palatal [ʝ̃]. In the Hupa velar nasal /ŋ/, the tongue often does not make full contact, resulting in a nasalized approximant, [ɰ̃]. This is cognate with a nasalized palatal approximant [ȷ̃] in other Athabaskan languages. In Umbundu, phonemic /ṽ/ contrasts with the (allophonically) nasalized approximant [w̃], and so is likely to be a true fricative rather than an approximant.[further explanation needed] In Old and Middle Irish, the lenited ⟨m⟩ was a nasalized bilabial fricative. Sundanese has an allophonic nasalized glottal stop [ʔ̃]; nasalized stops can only occur with pharyngeal articulation or lower, or else they'd be simple nasals. Nasal flaps are common allophonically. Many West African languages have a nasal flap [ɾ̃] (or [n̆]) as an allophone of /ɾ/ before a nasal vowel; Pashto, however, has a phonemic nasal retroflex lateral flap. Other languages, such as the Khoisan languages of Khoekhoe and Gǀui, as well as several of the !Kung languages, include nasal click consonants. Nasalization of these phonemes is denoted with a superscript ⟨ᵑ⟩ preceding the consonant (for example, ⟨ᵑǂ⟩).
Nareal consonants 
Besides nasalized oral fricatives, there are true nasal fricatives, called nareal fricatives, sometimes produced by people with speech defects. That is, the turbulence in the airflow characteristic of fricatives is produced not in the mouth but in the nasal cavity. A tilde plus trema diacritic is used for this in the Extensions to the IPA: [n͋] is an alveolar nareal fricative, with no airflow out of the mouth, while [v͋] is an oral fricative (a [v]) with simultaneous nareal frication. No known natural language makes use of nareal consonants.
Nasalization may be lost over time. There are also denasal sounds, which sound like nasals spoken with a head cold, but these are not used in non-pathological speech.
Contextual nasalization 
Vowels assimilate to surrounding nasal consonants in many languages, such as Thai, creating nasal vowel allophones. Some languages exhibit a nasalization of segments adjacent to phonemic or allophonic nasal vowels, such as Apurinã. Contextual nasalization can lead to the addition of nasal vowel phonemes to a language. This happened in French, where most final consonants disappeared, but where in the case of final nasals, the preceding vowels became nasal, introducing a new distinction into the language. An example where this happened is vin blanc [vɛ̃ blɑ̃] ('white wine'), ultimately from Latin vinum and blancum.
See also 
- Thurneysen, Rudolf; D. A. Binchy, Osborn Bergin (trans.) (1946). A Grammar of Old Irish. Dublin: Dublin Institute for Advanced Studies. p. 85. ISBN 1-85500-161-6.
- Ladefoged, Peter; Maddieson, Ian (1996). The Sounds of the World's Languages. Oxford: Blackwell. p. 134. ISBN 0-631-19814-8.
- Ladefoged, Peter; Maddieson, Ian (1996). The Sounds of the World's Languages. Oxford: Blackwell. p. 268. ISBN 0-631-19814-8.
- The World Atlas of Language Structures Online – Chapter 10 – Vowel Nasalization