ἀδελφή, -ῆς, ἡ (< ἀδελφός), [in LXX for אָהוֹת ;] a sister: Mat.19:29, al.; metaph. (MM, VGT, see word), of a member of the Christian community: Refs Rom.16:1, 1Co.7:15 Jas.21:15, al. (AS)
Thayer:
1) a full, own sister 2) one connected by the tie of the Christian religion
ἀδελφή
adelphē
ad-el-fay'
Feminine of G80; a sister (natural or ecclesiastical)
ἀδελφός
adelphos
ad-el-fos'
From G1 (as a connective particle) and δελφύς delphus (the womb); a brother (literally or figuratively) near or remote (much like [H1])
KJV Usage: brother.
G81 ἀδελφότηςἀδελφότης
adelphotēs
ad-el-fot'-ace
From G80; brotherhood (properly the feeling of brotherliness), that is, (the (Christian) fraternity
KJV Usage: brethren, brotherhood.
G5361 φιλάδελφοςφιλάδελφος
philadelphos
fil-ad'-el-fos
From G5384 and G80; fondofbrethren, that is, fraternal
KJV Usage: love as brethren.
G5569 ψευδάδελφοςψευδάδελφος
pseudadelphos
psyoo-dad'-el-fos
From G5571 and G80; a spuriousbrother, that is, pretendedassociate