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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 redundantly 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. (For example, 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, 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.〔(huh ). Collins American English Dictionary. HarperCollins Publishers Limited. Accessed October 4, 2014.〕 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'' "beautiful" and ''bon'' "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 .) The Portuguese words ''rim'' ("kidney") and ''ri'' ((he) "laughs", or (I) "laughed") differ only in that the former's vowel is nasal. Although loan words exist from French which contain nasal vowels (e.g. "croissant"), there is no expectation that an English speaker would have to nasalize these vowels to the extent French speakers do. Likewise, pronunciation keys in English dictionaries do not always indicate nasalization of French loan words. Diphthongs can also be nasalized. For example, the Portuguese pronunciation of the city of ''São Paulo'' uses the very common nasal diphthong ''ão'' (IPA: ). Its closest corresponding oral diphthong is ''au'' () (found in the word ''Paulo''), and is similar to the English ''ow'', as in ''now''. == Suprasegmental and transitional nasal vowels == In Min Chinese, nasal vowels carry persistent air flow through both the mouth and the nose, producing an invariant and sustainable vowel quality. That is, this type of nasalization is synchronic and suprasegmental to the voicing. In contrast, nasal vowels in French or Portuguese are transitional, where the velum ends up constricting the mouth airway. In languages that have transitional nasal vowels, it is common that there are fewer nasal vowels than oral ones. This appears to be due to a loss of distinctivity caused by the nasal articulation. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「nasal vowel」の詳細全文を読む スポンサード リンク
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