Dictionary entry

ὄρθρος

G. Abbott-Smith's A Manual Greek Lexicon of the New Testament

ὄρθρος, -ου, ὁ,

[in LXX for שַׁחַר, בֹּקֶר, etc.;]

daybreak, dawn: ὄρθρου βαθέως (M, Pr., 73), at early dawn, Lk 24:1; ὄρθρου, Jo 8:[2]; ὑπὸ τὸν ὄ., Ac 5:21 (cf. MM, xviii).†