Nasal Vowel

A nasal vowel is a vowel that is produced with a lowering of the velum so that air escapes both through nose as well as the mouth. By contrast, oral vowels are ordinary vowels without this nasalisation.

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, though few speakers would notice. This 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). However, the word "huh" is generally pronounced with a nasal vowel.

In French and Portuguese, by contrast, nasal vowels are phonemes distinct from oral vowels, since words that differ mainly in the nasal or oral quality of a vowel exist. 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/.)