Lexical Definition

‎δίκαιος‎ díkaios (dik'-ah-yos) just ^G:A
from ‎δίκη‎

just, meet, right(-eous).

• equitable (in character or act)
• by implication, innocent, holy (absolutely or relatively)

Abbott-Smith

δίκαιος, -α, -ον (< δίκη), [in LXX chiefly for צַדִּיק (for rendering of צַדִּיק in sense of correct, v. Deiss., BS, 115 f.); sometimes for נָקִי as Pr 1:11, al. ;]
in early Gk. writers
(a) of persons, observant of δίκη, custom, rule, right, righteous in performing duties to gods and men ;
(b) of things, righteous, in accordance with right.
In NT
1. righteous, chiefly in the broad sense, as above, of the person or thing corresponding to the Divine standard of right
(a) of persons: of God, Ro 3:26, I Jo 2:29 3:7; of Christ, Ac 3:14 7:52 22:14, I Pe 3:18, I Jo 2:1; of men, Mt 1:19 (Abbott, Essays, 75 f.) 10:41 13:17, 43, 49, Lk 1:6, 17, Ro 5:7, I Ti 1:9, Ja 5:6, I Pe 3:12, I Jo 3:7, Re 22:11, al.; δ. καὶ εὐλαβής, Lk 2:25; ἅγιος, Mk 6:20; ἀγαθός, Lk 23:50; φοβούμενος τ. θεόν, Ac 10:22; opp. to ἀμαρτωλοὶ καὶ ἀσεβεῖς, I Pe 4:18; ἄδικοι, Mt 5:45, Ac 24:15; δ. ἐκ πίστεως, Ro 1:17, Ga 3:11, He 10:38 (LXX); δ. παρὰ τ. θεῷ, Ro 2:13
(b) of things: ἔργα δ., opp. to πονηρὰ, I Jo 3:12; ἐντολή, Ro 7:12; metaph., αἷμα, Mt 23:35; τὸ δ., Lk 12:57; δ. ἐστιν, Ac 4:19, Eph 6:1, Phl 1:7; ὅ, Mt 20:4; ὅσα, Phl 4:8
2. In narrower sense
(a) of persons, as in later cl. writers, just, rendering to each his due: Tit 1:8, I Jo 1:9; δ. κριτής, II Ti 4:8
(b) of things: τὸ δ., Col 4:1; δ., sc. ἐστιν, II Th 1:6; κρίσις δ., Jo 5:30; ὁδοί, Re 15:3
SYN.: ἀγαθός (q.v.), καλός, χρηστός (Cremer, 183, 690).

Abbott-Smith References

Liddell-Scott-Jones

δίκαιος [ῐ], α, ον,

also ος, ον [Refs 5th c.BC+]: (δίκη):

__A in [Refs 8th c.BC+] and all writers, of persons, observant of custom or rule, [Refs 8th c.BC+]; especially of social rule, well-ordered, civilized, ὑβρισταί τε καὶ ἄγριοι οὐδὲ δ. [Refs 8th c.BC+]; δ. πολίτης a good citizen, [Refs 4th c.BC+]: metaphorically of the sea, [Refs 6th c.BC+]; δικαίη ζόη a civilized way of living, [Refs 5th c.BC+] adverb δικαίως, μνᾶσθαι woo in due form, decently, [Refs 8th c.BC+]loyally, [Refs 5th c.BC+]
__A.2 observant of duty to gods and men, righteous, [Refs 8th c.BC+]; opposed to δυσσεβής, [Refs 5th c.BC+]; also of actions, etc., righteous, ἐπὶ ῥηθέντι δικαίῳ a thing rightly said, [Refs 8th c.BC+]
__A.3 ὁ δίκαιος, euphemistic of a sacred snake, [Refs]
__B later:
__B.I equal, even, well-balanced, ἅρμα δίκαιον evengoing chariot, [Refs 5th c.BC+]; δικαιότατα μοχλεύειν [Refs]fair, impartial, βάσανος [Refs 5th c.BC+]
__B.I.b legally exact, precise, τῷ δικαιοτάτῳ τῶν λόγων to speak quite exactly, [Refs 5th c.BC+]; of Numbers, αἱ ἑκατὸν ὀργυιαὶ δίκαιαι [Refs 5th c.BC+]. adverb -αίως, πάντα δ. ὑμῖν τετήρηται [Refs 4th c.BC+]
__B.I.2 lawful, just, especially τὸ δ. right, opposed to τὸ ἄδικον, [Refs 5th c.BC+]; τὸ πολιτικὸν δ.[Refs 5th c.BC+]; τοὐμὸν δ. my own right, [Refs 5th c.BC+]; ἐλθεῖν ἐπὶ τοῦτο τὸ δ. bring the case to this issue, [Refs 5th c.BC+]; οὐδὲν τῶν δ. ποιεῖν τινί not to do what is just and right by a man, [Refs 5th c.BC+]; τὰ δ. ἔχειν, λαμβάνειν, receive one's due, [Refs]; τὰ δ. πράττεσθαι πόλιν give a city its deserts, [Refs 4th c.BC+]; ἐκ τοῦ δικαίου, ={δικαίως}, [Refs 5th c.BC+]; so ἀπὸ τοῦ δικαίου, τῶν δικαίων, [Refs 2nd c.BC+]; μετὰ τοῦ δ. [Refs 5th c.BC+]; τὸ δίκαιον lawful claim, ἃ ἔχομεν δίκαια πρός.. [Refs 5th c.BC+]; τὰ πρὸς ἀλλήλους δ. mutual obligations or contracts, [Refs 2nd c.BC+]; ἐπὶ συγκειμένοις τισὶ δικαίοις on certain agreed terms, [Refs 1st c.BC+]. adverb -αίως rightly, justly, [Refs 5th c.BC+]
__B.II of persons and things, meet and right, fitting, δ. τοῦδε τοῦ φόνου ῥαφεύς [Refs 4th c.BC+]; ἵππον δ. ποιεῖσθαί τινι make a horse fit for another's use, [Refs 5th c.BC+] having a good mouth, [Refs 2nd c.AD+]
__B.II.b normal, σχήματα [Refs 5th c.BC+]
__B.II.2 real, genuine, γόνος [Refs 5th c.BC+] adverb, εἴπερ δικαίως ἐστ᾽ ἐμός really and truly mine, [Refs 5th c.BC+]
__B.II.3 ὁ δ. λόγος the plea of equity, [Refs 5th c.BC+]. adverb -αίως with reason, [Refs 5th c.BC+]: comparative -ότερον[Refs 5th c.BC+] also -οτέρως [Refs 5th c.BC+]: superlative -ότατα[Refs 5th c.BC+]; Aeolic dialect δικαίτατα [Refs]
__B.III ψυχὴ ἐς τὸ δ. ἔβη 'the land of the leal', [Refs]
__C in Prose, δίκαιός εἰμι, with infinitive, δίκαιοί ἐστε ἰέναι you are bound to come, [Refs 5th c.BC+]; δ. εἰμι κολάζειν I have a right to punish, [Refs 5th c.BC+]; δ. εἰσι ἀπιστότατοι εἶναι they have most reason to distrust, [Refs 5th c.BC+]dignus est qui pereat, [Refs 4th c.BC+]; ὁ σπουδαῖος ἄρχειν δ. has a right to.., [Refs 4th c.BC+]; with a non-personal subject, ἔλεος δ. ἀντιδίδοσθαι [Refs 5th c.BC+]: less frequently in comparative and superlative, δικαιότεροι χαρίσασθαι [Refs 5th c.BC+]; but δίκαιόν ἐστι is also found, [Refs 5th c.BC+]; δικαίως ἄν, with optative, [Refs 5th c.BC+] with penultimate short in [Refs 5th c.AD+]; compare οὐ δίκαον· οὐ δίκαιον, [Refs 5th c.AD+]