ὀγδόατος
From LSJ
ὅτι τίς ὁ ἄνθρωπος, ὃς ἐπελεύσεται ὀπίσω τῆς βουλῆς τὰ ὅσα ἐποίησεν αὐτήν; (Ecclesiastes 2:12, LXX version) → for who is the man who, after following his own plan, will find wisdom (in) everything he has done?
English (LSJ)
η, ον, poet. for ὄγδοος, as τρίτατος for τρίτος,
A the eighth, Il.19.246, Od.3.306, Emp. 68 ; ὀ. δεκάς Rev.Phil.22.357 ; ἡ ὀγδοάτη (sc. ἡμέρα) the eighth day, octave, Hes.Op.772, 790 (καθ' ὁγδοάδην δεκάδα prob. in Jahresh.23 Beibl.402 (Egypt)).
German (Pape)
[Seite 290] poet. = ὄγδοος, der achte (vgl. τρίτατος u. ἑβδόματος mit τρίτος u. ἕβδομος), Il. 19, 248 Od. 3, 306. 4, 82, Hes. O. 774.