Monophthongs, dyphthongs and triphthongs are types of?
Vowel 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 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 , the vowel sound in "boy" is in most dialects a diphthong , and
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