diphthong(n = noun.communication) - a vowel sound that starts near the articulatory position for one vowel and moves toward the position for another;
is a kind of vowel, vowel sound
Derived form verb diphthongize₁

diphthong, n.
1 a speech sound in one syllable in which the articulation begins as for one vowel and moves as for another (as in coin, loud, and side).
2 a a digraph representing the sound of a diphthong or single vowel (as in feat). b a compound vowel character; a ligature (as {aelig}).

Derivative:
diphthongal adj.

Etymology:
F diphtongue f. LL diphthongus f. Gk diphthoggos (as DI-(1), phthoggos voice)

N  letter, character, hieroglyphic, type, capitals, digraph, trigraph, ideogram, ideograph, majuscule, minuscule, majuscule, minuscule, alphabet, ABC, abecedary, christcross-row, consonant, vowel, diphthong, triphthong, mute, liquid, labial, dental, guttural, syllable, monosyllable, dissyllable, polysyllable, affix, suffix, spelling, orthograph, phonography, phonetic spelling, anagrammatism, metagrammatism, cipher, monogram, anagram, doubleacrostic, literal, alphabetical, abecedarian, syllabic, majuscular, minuscular, uncial.