A monophthong (Greek μονόφθογγος, "monophthongos" = single note) is a "pure" vowel sound, one whose articulation at both beginning and end is relatively fixed, and which doesn't glide up or down towards a new position of articulation; compare diphthong. The conversion of monophthongs to diphthongs (diphthongization) or of diphthongs to monophthongs (monophthongization), is a major element of language change and is likely the cause of furth… (More on Monophthong)