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.