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. By contrast,
oral vowels are vowels without this 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).