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 different syllables.