noun Historical Linguistics.
the lengthening of a vowel when a following consonant is weakened or lost, as the change from Old English niht /nɪxt/ [nikht] Show IPA
to night /naɪt/ [nahyt] Show IPA
with loss of /x/ [kh] Show IPA
and lengthening of /ɪ/ [i] Show IPA
to a vowel that eventually became /aɪ/ [ahy] Show IPA .