Diphthong

A diphthong is a vowel sound that glides from one vowel quality to another within a single syllable. Its articulation changes during the sound, unlike a pure vowel’s.

Vowel: A speech sound produced with an open vocal tract and no constriction that blocks airflow. A diphthong is a changing kind of vowel sound.
International Phonetic Alphabet: A standardized alphabet for representing speech sounds across languages. Its symbols can mark both the starting and ending qualities of a diphthong.
English phonology: The sound system and sound-pattern rules of the English language. English has several diphthongs, though their exact realizations vary by dialect.
Hiatus: The sequence of adjacent vowels pronounced in separate syllables. A diphthong changes vowel quality within one syllable; hiatus separates vowels across syllables.
Formant: A resonant frequency band in the acoustic spectrum of a voiced speech sound. Formant movement provides measurable evidence of a diphthong’s changing vowel quality.
Phonetics: The study of speech sounds, including their production, acoustic properties, and perception. Diphthongs are described through their articulation and acoustic shape.
Received Pronunciation: A historically prestigious accent of British English with a well-described vowel system. Its vowel inventory provides familiar examples of English diphthongs.
Vowel sequence: Two or more adjacent vowel sounds whose syllabification depends on a language’s sound patterns. Not every adjacent pair of vowel qualities forms a single-syllable diphthong.
Vowel height: The vertical position of the tongue body during the production of a vowel. A diphthong may glide between vowel qualities with different tongue heights.
Phonology: The study of how speech sounds function and pattern within languages. Languages differ in which diphthongs they treat as distinct sound units.

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