There are seven vowels: α, ε, η, ι, ο, υ, ω. Of these ε and ο are always short, and take about half the time to pronounce as η and ω, which are always long; α, ι, υ are short in some syllables, long in others. In this Grammar, when α, ι, υ are not marked as long (ᾱ, ῑ, ῡ) they are understood to be short. All vowels with the circumflex (149) are long. On length by position, see 144.
a. Vowels are said to be open or close according as the mouth is more open or less open in pronouncing them, the tongue and lips assuming different positions in the case of each.