Quick Definition
early dawn, day-break
Strong's Definition
dawn (as sun-rise, rising of light); by extension, morn
Derivation: from the same as G3735 (ὄρος);
KJV Usage: early in the morning
Thayer's Greek Lexicon
ὄρθρος, ὄρθρου, ὁ (from ὈΡΩ, ὄρνυμι to stir up, rouse; cf. Latinorior,ortus), from Hesiod down; the Sept. for ωΗΡηΗψ dawn, and several times for αΙΜχΖψ; daybreak, dawn: ὄρθρου βαθέος or βαθέως (see βαθέως and βαθύς (on the genitive cf. Winers Grammar, § 30, 11; Buttmann, § 132, 26)), at early dawn, Luk_24:1; ὄρθρου, at daybreak, at dawn, early in the morning, Joh_8:2 (Hesiod, Works, 575; the Sept. Jer_25:4; Jer_33:5 (), etc.); ὑπό τόν ὄρθρον, Act_5:21 (Dio Cassius, 76, 17).
Mounce Concise Greek Dictionary
ὄρθρος orthros 3x
the dawn; the morning, Joh_8:2 ; Act_5:21 ;
ὄρθος βαθύς , the first streak of dawn, the early dawn, Luk_24:1
Abbott-Smith Greek Lexicon
ὄρθρος , -ου , ὁ ,
[in LXX for H7837 , H1242 , etc.;]
daybreak, dawn: ὄρθρου βαθέως ( M , Pr., 73), at early dawn, Luk_24:1 ; ὄρθρου , Joh_8:2 ; ὑπὸ τὸν ὄ ., Act_5:21 ( cf. MM , xviii).†
Moulton & Milligan — Vocabulary of the Greek NT
ὄρθρος [page 457]
P Fay 108 .10 ( c. A.D. 171) ὑπὸ τὸν ὄρθρον , about dawn, the same phrase as in Act_5:21 : cf. P Flor III. 305 .11 (iv/A.D.) ὄρθρου , di buon mattino (Ed.).
Liddell-Scott — Intermediate Greek Lexicon
ὄρθρος ὄρθρος, ὁ, "day-break, dawn, cock-crow", Hhymn. , Ar. ; ὄρθρου "at dawn", Hes. ; ὄρθρου γενομένου Hdt. ; ἅμα ὄρθρῳ id=Hdt. , etc.; also, τὸν ὄρθρον, absol., "in the morning", id=Hdt. ; δι᾽ ὄρθρων each "morning early", Eur. :— ὄρθρος βαθύς early "dawn", just before daybreak, Ar. , Plat.
STEPBible — Tyndale Abridged Greek Lexicon
ὄρθρος, -ου, ὁ
[in LXX for שַׁחַר, בֹּקֶר, etc. ;]
daybreak, dawn: ὄρθρου βαθέως (M, Pr., 73), at early dawn, Luk.24:1; ὄρθρου, Jhn.8:2; ὑπὸ τὸν ὄ., Act.5:21 (cf. MM, xviii).†
(AS)