A nasal vowel is a vowel that is produced with a lowering of the velum so that air escapes both through the nose as well as the mouth, such as the French vowel . By contrast, oral vowels are vowels without the nasalization. As explained below, nasal vowels that are distinctive or obligatory are of far more linguistic importance than whether or not speakers of a language tend to nasalize vowels in some instances. Relatively similar languages in the same branch of a language family differ on this point quite frequently throughout the world such as in Spanish and Portuguese.
In most languages, vowels that are adjacent to nasal consonants are produced partially or fully with a lowered velum in a natural process of assimilation and are therefore technically nasal, but few speakers would notice. That is the case in English: vowels preceding nasal consonants are nasalized, but there is no phonemic distinction between nasal and oral vowels (and all vowels are considered phonemically oral).
In French and Portuguese, by contrast, nasal vowels are phonemes distinct from oral vowels since words can differ mainly in the nasal or oral quality of a vowel. For example, the French words beau /bo/ "beautiful" and bon /bõ/ "good" differ only in that the former is oral and the latter is nasal. (To be more precise, the vowel in bon is slightly more open, leading many dictionaries to transcribe it as /ɔ̃/.)
The Portuguese words rim ("kidney") and ri ((he/she/it/you) "laughs/laugh", or (I) "laughed") differ only in that the former's vowel is nasal. Although loanwords exist from French that contain nasal vowels ("croissant"), there is no expectation that an English-speaker would nasalize the vowels to the extent that French speakers do. Likewise, pronunciation keys in English dictionaries do not always indicate nasalization of French loanwords.
Also, diphthongs can be nasalized. For example, the Portuguese pronunciation of the city of São Paulo uses the very common nasal diphthong ão (IPA: /ɐ̃w̃/). Its closest corresponding oral diphthong is au [aw] (found in the word Paulo) and is similar to the English ow, as in now.
Vowel height and nasalization
Nasalization may cause a vowel's articulation to shift. However, nasalization from the assimilation of a nasal consonant tends to cause a raising of vowel height; phonemically distinctive nasalization tends to lower the vowel.
A few languages, such as Palantla Chinantec, contrast lightly nasalized and heavily nasalized vowels. They may be contrasted in print by doubling the IPA diacritic for nasalization: ⟨ẽ⟩ vs ⟨ẽ̃⟩. Bickford & Floyd (2006) combine the tilde with the ogonek: ⟨ẽ⟩ vs ⟨ę̃⟩. (The ogonek is sometimes used in an otherwise IPA transcription to avoid conflict with tone diacritics above the vowels.)
Languages that are written in the Latin alphabet may indicate nasal vowels by a trailing silent n or m, as is the case in French, Portuguese, Lombard (central classic orthography), Bamana, or Yoruba. In other cases, they are indicated by diacritics: Portuguese also marks nasality with a tilde, ã, õ, before other vowels; Breton indicates a nasal vowel by a silent trailing ñ with tilde, as in bezañ, "to be"; Polish, Navajo, and Elfdalian use a hook under the letter, called an ogonek, as in ą, ę.
Other languages may use a superscript n (aⁿ, eⁿ, ...), as in the Pe̍h-ōe-jī romanization of Southern Min. In the International Phonetic Alphabet, nasal vowels are denoted by a tilde over the symbol for the vowel, as in Portuguese.
The Nasta'liq script, used by Urdu, denotes nasalization by employing the Arabic letter ˂ن˃ nūn but removing the dot (˂ں˃), called nūn ghunna. Nasalized vowels occur in Classical Arabic but not in contemporary speech or Modern Standard Arabic. There is no orthographic way to denote the nasalization, but it is systematically taught as part of the essential rules of tajweed, used to read the Qur'an. Nasalization occurs in recitation, usually when a final ˂ن˃ nūn is followed by a ˂ي˃ yāʼ.
Examples of languages
These languages use phonemic nasal vowels:
- Bengali (Nasalization is weak in Indian Bengali, and mostly absent in Bangladeshi Bengali).
- Dutch Low Saxon
- French (see French phonology)
- German (French loanwords of some speakers, Austro-Bavarian and Swabian dialects)
- Gbe languages
- Gheg Albanian
- Haitian Creole
- Malay (Kelantan-Pattani, Terengganu, and Pahang dialects)
- Marathi (only old Marathi, but not the contemporary language. See Marathi phonology.)
- Hokkien (including Taiwanese)
- Munda languages
- Paicî (an unusually large number of nasal vowels)
- Polish (most dialects)
- Tamil (modern Colloquial Tamil only; Literary Tamil uses oral-vowel plus nasal-stop sequences instead)
- Wu (including Shanghainese)
- Yélî Dnye (an unusually large number of nasal vowels)
- Mande languages
- Surinamese Creoles (Sranan Tongo, Ndyuka language, Saramaccan language, Jamaican Maroon spirit-possession language)
- Krio language
- Basilectal Western Caribbean creole languages (Jamaican Patois, Belize Kriol, San Andres y Providencia Creole)
- huh. Collins American English Dictionary. HarperCollins Publishers Limited. Accessed October 4, 2014.
- Beddor, P. S. 1983. Phonological and phonetic effects of nasalization on vowel height
- The World Atlas of Language Structures Online - Chapter 10 - Vowel Nasalization
- Juliette Blevins (2004). Evolutionary Phonology: The Emergence of Sound Patterns. Cambridge University Press. p. 203.