Vowel the vowel sounds of "flower", , form a triphthong or disyllable, depending on dialect. In phonology, diphthongs and triphthongs are distinguished from sequences of monophthongs by whether the vowel sound may be analyzed into different phonemes or not. For example, the vowel sounds in a two-syllable pronunciation of the word "flower" () phonetically form a disyllabic triphthong, but are phonologically a sequence of a diphthong (represented by the letters ) and a monophthong (represented by the letters ). Some linguists use the terms "diphthong" and "triphthong" only in this phonemic sense. The name "vowel" is often used for the symbols
Vietnamese language same applies to the vowels long "a" and short "ă" . The centering diphthongs are formed with only the three high vowels ("i", "ư", "u"). They are generally spelled as "ia", "ưa", "ua" when they end a word and are spelled "iê", "ươ", "uô", respectively, when they are followed by a consonant. In addition to single vowels (or monophthongs) and centering diphthongs, Vietnamese has closing diphthongs and triphthongs. The closing diphthongs and triphthongs consist of a main vowel component followed by a shorter semivowel offglide or . There are restrictions on the high offglides: cannot occur after a front vowel