Υυ · Yy — LSJ
hy
twenty-third letter of the Formello abecedarium, IG 14.2420, but twentieth of the Ion. alphabet: as numeral υʹ = 400, but ͵υ = 400,000. It is called τὸ ὖ by Pl. Cra. 393d, Callias ap. Ath. 10.453d (prob., the line ends ταῦ, <τὸ> ὖ), IG 2(2).2783.4 (iv B. C.), Hellad. ap. Phot. Bibl. p.530 B.; τό τʼ ὖ or τό θʼ ὗ might be read in Achae. 33.3 for τοῦ ῡ codd. Ath.; later τὸ υ ψιλόν or τὸ ψιλὸν υ (as name of the first letter of ὕαλος, υἱός, etc.), Theognost. Can. 18, Sch. Ar. Pl. 896, Ps. Hdn. Epim.