Quick Definition
dawn
Strong's Definition
relating to the dawn, i.e. matutinal (as an epithet of Venus, especially brilliant in the early day)
Derivation: from G3722 (ὄρθρος);
KJV Usage: morning
Thayer's Greek Lexicon
ὀρθρινός, -7, -όν, (fr. ὄρθρος ; cf. ἡμερινός, ἑσπερινός, ὀπωρινός, mpwivds), a poetic [Anth.] and later form for ὄρθριος (see Lob. ad Phryn. p. 51; Siurz, De dial. Maced. et Alex. p. 186; [W. 25]), early: Rev. xxii. 16 Ree.; Lk. xxiv. 22 LTTrWH. (Hos. vi. 4; Sap. xi. 23 (22).)
Mounce Concise Greek Dictionary
ὀρθρινός orthrinos 1x
a later form of ὄρθριος, of or belonging to the morning, morning, Lk. 24:22*
Abbott-Smith Greek Lexicon
† ὀρθρινός, -ή, -όν
(< ὄρθρος), [in LXX: Ho 6: (4) 13:3 (שׁכם hi.), Hg 2:15 (14), Wi 11:22*;] late form of ὄρθριος (q.v.),
early: Lk 24:22.†
Moulton & Milligan — Vocabulary of the Greek NT
Liddell-Scott-Jones — Greek-English Lexicon
ὀρθρινός (orthrinos) — dawn. ὀρθρ-ινός, ή, όν, (ὄρθρος) later form [LXX+5th c.BC+]; ὀρθρινὸς οἴχεσθαι [Refs 1st c.BC+] adverb, ὀρθρινὰ παίζειν[Refs 4th c.BC+], etc. make ι long, probably in imitation of ὀπωρῑνῷ which is a metrically necessity in [Refs 8th c.BC+]