A nasal vowel is a vowel that produced with a lowering of the velum so that air escapes both through the mouth and the nose.
In many languages, vowels that are adjacent to nasal consonants are produced partially or fully with a lowered velum. In English, vowels preceding nasal consonants are nasalized, but there is no phonemic distinction between nasal and oral vowels (all vowels are considered phonemically oral).
In French, nasal vowels have phonemic status, since words can differ only in whether a vowel is nasalized or not. For example, the words sait "knows" and saint "saint" are pronounced the same, except the vowel in saint is nasal and the vowel in sait is oral.
Many languages do not have phonemic nasal vowels. For those that have them, it is commonly the case that there are less nasal vowels than oral ones. This appears to be caused by the loss of distinctivity produced by the nasal articulation.
Occurs in: