Lexical Definition

‎ἀδελφός‎ adelphós (ad-el-fos') brother G:N-M
from ‎Α‎ (as a connective particle) and (the womb)

brother.

Usage: 30 forms in 1002 verses

Abbott-Smith

ἀδελφός, -οῦ, ὁ (< ἀ- copul., δελφύς, womb),
in cl., a brother, born of the same parent or parents. [In LXX (Hort, Ja., 102 f.), for אָח;]
1. lit. of a brother (Ge 4:2, al.).
2. Of a neighbour (Le 19:17).
3. Of a member of the same nation (Ex 2:14, De 15:3). In NT in each of these senses (1. Mt 1:2, al.; 2. Mt 7:3; 3. Ro 9:3) and also,
4. of a fellow-Christian: I Co 1:1, Ac 9:30. This usage finds illustration in π., where ἀ. is used of members of a pagan religious community (M, Th., I, 1:4; MM, VGT, s.v.). The ἀδελφοὶ τ. Κυρίου (Mt 12:46-49 13:55 28:10, Mk 3:31-34, Lk 8:19-21, Jo 2:12 7:3, 5 10 20:17, Ac 1:14, I Co 9:5) may have been sons of Joseph and Mary (Mayor, Ja., Intr. viff.; DB, i, 320 ff.) or of Joseph by a former marriage (Lft., Gal., 252ff.; DCG, i, 232 ff.), but the view of Jerome, which makes ἀ. equivalent to ἀνεψιός, is inconsistent with Greek usage. (Cremer, 66.)

Abbott-Smith References

Book Refs
Genesis 4:2
Exodus 2:14
Leviticus 19:17
Deuteronomy 15:3
Matthew 1:2 · 7:3 · 12:46 · 13:55 · 28:10
Mark 3:31
Luke 8:19
John 2:12 · 7:3 · 7:5 · 7:10 · 20:17
Acts 1:14 · 9:30
Romans 9:3
1 Corinthians 1:1 · 9:5

Liddell-Scott-Jones

ἀδελφός [],

(- copulative, δελφύς, [Refs 4th c.BC+]; compare ἀγάστωρ) properly, son of the same mother:

__I as substantive, ἀδελφός, , vocative ἄδελφ; Epic dialect, Ionic dialect, and Lyric poetry ἀδελφεός (genitive -ειοῦ in [Refs 8th c.BC+]:—brother, [Refs 8th c.BC+]; ἀδελφοί brother and sister, [Refs 5th c.BC+]; so of the Ptolemies, θεοὶ ἀδελφοί[Refs 3rd c.BC+]; ἀπ᾽ ἀμφοτέρων ἀδελφεός[LXX+5th c.BC+]
__I.2 kinsman,[LXX]; tribesman, Ex.[Refs]
__I.3 colleague, associate, [Refs]; member of a college, [Refs]
__I.4 term of address, used by kings, [LXX+2nd c.BC+], etc.:—as a term of affection, applicable by wife to husband, [LXX+2nd c.BC+]
__I.5 brother (as a fellow Christian), [NT]; of other religious communities, e.g. Serapeum, [Refs 2nd c.BC+]
__I.6 metaphorically, of things, fellow, ἀνὴρ τῷ . προσκολληθήσεται, of Leviathan's scales, [LXX]
__II adjective, ἀδελφός, , όν, brotherly or sisterly, [Refs 4th c.BC+]; φύσιν . ἔχοντες, of Hephaistos and Athena, [Refs 5th c.BC+]
__II.2 generally, of anything double, twin, in pairs, [Refs 5th c.BC+]:—also, akin, cognate, μαθήματα[Refs 5th c.BC+]

LSJ Scripture Refs: LXX.Job.30.29LXX.Gen.13.8Matt.12.50Acts.9.30LXX.Job.41.8*