A combination of three vowel sounds in a single syllable, forming a simple or compound sound; also, a union of three vowel characters, representing together a single sound; a trigraph; as, eye, -ieu in adieu, -eau in beau, are examples of triphthongs.

A single syllable consisting of three consecutive vowel sounds.

A group of three vowels in the same syllable. In Spanish, this only happens in cases of sinalefa (eg e hoy).

A group of 3 vowels which are pronounced together as a single syllable

In phonetics, a triphthong (Greek τρίφθογγος, "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.