Vowel
Monophthongs, diphthongs, triphthongs

A vowel sound whose quality does not change throughout 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 successively through three qualities is a triphthong.

All languages have monophthongs and many languages have diphthongs, but triphthongs or vowel sounds with even more target qualities are relatively rare cross-linguistically. English has all three types: the vowel sound in hit is a monophthong /ɪ/, the vowel sound in boy is in most dialects a diphthong /ɔɪ/, and the vowel sounds of flower, /aʊər/, form a triphthong or disyllable, depending on the dialect.

In phonology, diphthongs and triphthongs are distinguished from sequences of monophthongs by whether the vowel sound may be analyzed into distinct phonemes. For example, the vowel sounds in a two-syllable pronunciation of the word flower (/ˈflaʊər/) phonetically form a disyllabic triphthong but are phonologically a sequence of a diphthong (represented by the letters ⟨ ow ⟩) and a monophthong (represented by the letters ⟨ er ⟩). Some linguists use the terms diphthong and triphthong only in this phonemic sense.
language:response_language[Polish], length_constraints:number_sentences[15], punctuation:no_comma