The Greek noun adelphotēs (ἀδελφότης) means brotherhood — the whole body of brothers and sisters, the fraternity of believers. It is an abstract noun formed from adelphos (brother), describing not just individual brothers but the corporate community of brotherhood itself. It appears only twice in the New Testament, both times in 1 Peter: 2:17 ("love the brotherhood") and 5:9 ("your brothers and sisters throughout the world"). It was also used in Maccabean literature for the solidarity of Israel's warriors.
Peter's command to "love the adelphotēs" (1 Peter 2:17) is a call to love not just individual brothers and sisters but the communal reality of the family of God — the brotherhood as a whole. This has profound implications for how Christians relate to the universal church. The second use (1 Peter 5:9) is remarkable in context: "Resist the devil, standing firm in the faith, because you know that your brothers and sisters (adelphotēs) throughout the world are undergoing the same kind of sufferings." Brotherhood is forged in shared suffering. This is the same truth military brotherhood embodies: the bond is not formed in easy days but in the crucible of shared hardship. The adelphotēs of the church is a global fellowship of those who suffer together, stand together, and will be restored together (1 Peter 5:10).