diphthongs

Diphthongs are vowel sounds that begin with one vowel and glide to another within the same syllable. The articulation involves movement of the tongue from the position of the initial vowel toward the position of the final vowel during the vowel’s duration. This dynamic quality distinguishes diphthongs from monophthongs, which maintain a single vowel height and quality throughout the syllable. In phonology, a diphthong is typically treated as a single phoneme with changing quality, rather than as two separate vowels.

In many languages, diphthongs can function as single phonemes distinct from pure vowels. In English, the core five rising diphthongs are commonly cited: /eɪ/ as in face, /aɪ/ as in price, /ɔɪ/ as in choice, /aʊ/ as in mouth, and /oʊ/ (or /əʊ/) as in go. Some dialects also have centering or trailing variants such as /ɪə/ in near or /eə/ in air. The exact realization of these sounds varies by dialect; for example, General American often uses /eɪ, aɪ, ɔɪ, aʊ, oʊ/.

Beyond English, diphthongs occur in many languages with varying inventories. Some languages have many diphthongs, while others rely largely on monophthongs. Diphthongs can be phonemic, distinguishing words, or they can arise as phonetic realizations of sequences of vowels. Diachronically, languages may undergo diphthongization, creating new diphthongs, or monophthongization, reducing them.