ὐψιλόν

Middle Liddell

Υ, υ, τό, indecl., twentieth letter of Gr. alphabet: as numeral υ# = 400, but #22υ = 400, 000. Called ὑψιλόν, because the orig. sound was broad, like ου, and afterwards was thin like French u. The Gr. υ, like Lat. v, was originally both a vowel (u) and a semi-vowel (v), v. infr. II.
I. Interchanges of υ with other vowels,
1. aeolic for ο, as ὄνυμα στύμα ὔρνις for ὄνομα στόμα ὄρνις; also πίσυρες for πέτορες (τέσσαρεσ), cf. νύξ, Lat. nox.
2. aeolic, the diphth. ου became οι, Μοῖσα for Μοῦσα, λέγοισα for λέγουσα.
3. ῡ sometimes replaces οι, as κοινός ξυνός, κοίρανος κύριος.
4. Boeot. ῡ for ω, as χελύνη for χελώνη.
II. υ as a semivowel represented vau (ϝ), the digamma, sometimes it formed the diphth. αυ, as αὐέρυσαν for ἀνϝέρυσαν (v. αὐερύὠ, αὐίαχοι for ἀνϝίαχοι, αὐάτα for ἀϝάτα (ἄτἠ, καλαῦροψ for καλάϝροψ, ταλαύρινος for ταλάϝρινος, ταναύποδες for ταναϝόποδες; sometimes the dipth. ευ, as εὔαδεν for ἔϝαδεν.