Vowel breaking was completely absent in Portuguese.

Vowel breaking of "è" in closed syllables.

'Vowel breaking"', or "'fracture"', caused a front vowel to be split into a semivowel-vowel sequence before a back vowel in the following syllable.

Vowel breaking is often distinguished from diphthongization and defined more narrowly as a harmonic (i.e., assimilatory) process involving diphthongization triggered by a following vowel or consonant.