Webster 1913 Edition
(?; 115, 277),
diphthongus, Gr. [GREEK];
δίσ-twice + [GREEK] voice, sound, fr. [GREEK] to utter a sound: cf. F.
A coalition or union of two vowel sounds pronounced in one syllable; as, ou in out, oi in noise; – called a
A vowel digraph; a union of two vowels in the same syllable, only one of them being sounded; as, ai in rain, eo in people; – called an
To form or pronounce as a diphthong; diphthongize.