Hi omg! ?dif?THäNG,?dip-,-?THôNG/ noun 1. a sound formed by the combination of two vowels in a single syllable, in which the sound begins as one vowel and moves toward another (as in coin and loud) *from Google definitions.
It's actually fun to play with these. Say "coin" very slowly. You'll feel both vowels slide into one another within the syllable.