Definition of diphthong
1
linguistics
: a gliding (see glide entry 1 sense 4) monosyllabic speech sound (such as the vowel combination at the end of toy) that starts at or near the articulatory position for one vowel and moves to or toward the position of another
3
: the ligature (see ligature sense 4) æ or œ
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Merriam-Webster unabridged
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Time Traveler for diphthong
The first known use of diphthong was in the 15th century
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