A.son of the same mother:
I. as Subst., ἀδελφός, ὁ, voc. ἄδελφε; Ep., Ion., and Lyr. ἀδελφεός (gen. -ειοῦ in Hom. is for -εόο), Cret. ἀδελφιός, ἀδευφιός, Leg.Gort.2.21, Mon.Ant.18.319:—brother, Hom., etc.; ἀδελφοί brother and sister, E.El.536; so of the Ptolemies, “θεοὶ ἀδελφοί” Herod.1.30, OGI50.2 (iii B. C.), etc.; “ἀπ᾽ ἀμφοτέρων ἀδελφεός” Hdt.7.97: prov., “χαλεποὶ πόλεμοι ἀδελφῶν” E.Fr.975: metaph., “ἀ. γέγονα σειρήνων” LXX Jb.30.29.
3. colleague, associate, PTeb.1.12, IG12 (9).906.19 (Chalcis); member of a college, ib.14.956.
4. term of address, used by kings, OGI138.3 (Philae), J.AJ13.2.2, etc.; generally, LXX Ju.7.30; esp. in letters, PPar.48 (ii B. C.), etc.:—as a term of affection, applicable by wife to husband, LXX To.10.12, PLond.1.42.1 (ii B. C.), etc.
5. brother (as a fellow Christian), Ev.Matt.12.50, Act.Ap.9.30, al.; of other religious communities, e.g. Serapeum, PPar.42.1 (ii B. C.), cf. PTaur.1.1.20.
6. metaph., of things, fellow, ἀνὴρ τῷ ἀ. προσκολληθήσεται, of Leviathan's scales, LXX Jb.41.8.
II. Adj., ἀδελφός, ή, όν, brotherly or sisterly, A.Th. 811, etc.; φύσιν ἀ. ἔχοντες, of Hephaistos and Athena, Pl.Criti. 109c.
2. generally, of anything double, twin, in pairs, X.Mem. 2.3.19:—also, akin, cognate, “μαθήματα” Archyt.1; “ἀ. νόμοις” Pl.Lg. 683a: mostly c. gen., “ἀδελφὰ τῶνδε” S.Ant.192; “ἡ δὲ μωρία μάλιστ᾽ ἀ. τῆς πονηρίας ἔφυ” Id.Fr.925; freq. in Pl., Phd.108b, Cra.418e, al., cf. Hyp.Epit.35: c. dat., “ἀδελφὰ τούτοισι” S.OC1262, cf. Pl.Smp.210b.