A diphthong is a vowel in which there is a noticeable sound change within the same syllable. "Diphthong" originates from the Greek for "two voices" or "two sounds." A diphthong creates a unique sound as its two vowel sounds glide together.

A diphthong (/ ˈ d ɪ f θ ɒ ŋ, ˈ d ɪ p-/ DIF-thong, DIP-; [1] from Ancient Greek δίφθογγος (díphthongos) ' two sounds ', from δίς (dís) ' twice ' and φθόγγος (phthóngos) ' sound '), also known as a gliding vowel or a vowel glide, is a combination of two adjacent vowel sounds within the same syllable. [2]