Strong's G81 — ἀδελφότης (noun)
adelphotes (ad-el-fot'-ace) n.
1. (properly) the feeling of brotherliness
2. (commonly) brotherhood,  i.e. the (Christian) fraternity
[from G80]
KJV: brethren, brotherhood 
Root(s): G80 
Hebrew root: ἀδελφός
Occurrences: 2