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
Monophthong to monophthongs (monophthongization), are major elements of language change and are likely the cause of further changes. In some languages, due to monophthongization, graphemes that originally represented diphthongs now represent monophthongs. Monophthong A monophthong ( Greek "monóphthongos" from "mónos" "single" and "phthóngos" "sound") is a pure vowel sound, one whose articulation at both beginning and end is relatively fixed, and which does not glide up or down towards a new position of articulation. The monophthongs can be contrasted with diphthongs, where the vowel quality changes within the same syllable, and hiatus, where two vowels are next to each other in