I.a brotherhood: in Hom. a people of kindred race, a tribe, clan, κρῖν᾽ ἄνδρας κατὰ φρήτρας, ὡς φρήτρη φρήτρῃφιν ἀρήγῃ choose men by clans, that clan may stand by clan, Il.
II.at Athens, the φρατρία was a subdivision of the φυλή, as at Rome the curia of the tribus, Isocr., etc.: every φυλή consisted of three φρατρίαι, whose members were called φράτερες or φράτορες (as those of a φυλή were φυλέται): every φρατρία contained 30 γένη, so that by Solon.'s constitution Athens had 12 φρατρίαι, and 360 γένη or old patrician houses.
From the same Root as Lat. frater.