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).