In words consisting of 3 syllables with a, o, u in the first, stressed syllable, u in the second syllable and i in third syllable, the vowels of the first two syllables were affected by palatal mutation.
a, o, u │u│i
OS arundi > OE ærende
OS saturnidæ™ > OE sæterndæ™
Traces of palatal mutation are observed in Modern English.
a) In some plurals of nouns:
foot – feet
b) In some abstract nouns formed from adjectives:
strong – strength
c) In verbs formed from nouns:
food – feed
d) In verbs formed from adjectives:
full – fill
e) In the comparatives of the adjectives:
old – elder – eldest.
Back Umlaut (orVerbal Umlaut)
Front vowels æ, i, u turned into diphthongs if the following syllable contained a back vowel (a, o, u).
æ > ea caru > cearu ( care)
e > eo hefon > heofon (heaven)
i > io silufr > siolufr (silver)
