from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. Alternation of sounds within a word that indicates grammatical information (often inflectional).
from The Century Dictionary and Cyclopedia
- n. Vowel-gradation; the vowel-differentiation of words known as ablaut (which see).
From French apophonie, from apo- + Ancient Greek φωνή (phone, "sound"). (Wiktionary)