There are two complementary definitions of vowel, one phonetic and the other phonological.
• In the phonetic definition, a vowel is a sound, such as the English "ah" /ɑː/ or "oh" /oʊ/,

The acoustics of vowels are fairly well understood. The different vowel qualities are realized in acoustic analyses of vowels by the relative values of the formants, acoustic resonances of the vocal tract which show up as dark bands on a spectrogram.

A vowel sound whose quality does not change over the duration of the vowel is called a monophthong. Monophthongs are sometimes called "pure" or "stable" vowels. A vowel sound that glides from one quality to another is called a diphthong, and a vowel sound that glides

The importance of vowels in distinguishing one word from another varies from language to language. Nearly all languages have at least

The traditional view of vowel production, reflected for example in the terminology and presentation of the International Phonetic Alphabet, is one of articulatory features that

In addition to variation in vowel quality as described above, vowels vary as a result of differences in prosody. The most important prosodic variables are pitch (fundamental frequency

The name "vowel" is often used for the symbols that represent vowel sounds in a language's writing system, particularly if the language uses an alphabet. In writing systems based on the Latin alphabet, the letters A, E, I, O, U, Y, W and sometimes others can all be used to