The
mos maiorum ("ancestral custom" or "way of the elders," plural
mores, with
maiorum a
genitive plural; cf. English "
mores") is the unwritten code from which the
ancient Romans derived their
social norms. It is the core concept of Roman traditionalism, distinguished from but in dynamic complement to
written law. The
mos maiorum was collectively the time-honoured principles, behavioural models, and social practices that affected private, political, and military life in ancient Rome.