Shortening of long vowels

Shortening.—A long vowel may be shortened before another long vowel: βασιλέων from βασιλήων of kings, νεῶν from νηῶν of ships, τεθνεώς from τεθνηώς dead.

A long vowel before ι, υ, a nasal, or a liquid + a following consonant was regularly shortened: νᾰῦς from original νᾱυς ship, ἐμίγεν from ἐ-μιγη-ντ were mixed. The long vowel was often introduced again, as Ion. νηῦς ship.