In phonetics, a triphthong (Greek Ï„Ïίφθογγος, "triphthongos", literally "with three sounds," or "with three tones") is a monosyllabic vowel combination usually involving a quick but smooth movement from one vowel to another that passes over a third one. While "pure" vowels, or monophthongs, are said to have one target tongue position, triphthongs have a moving tongue.