The mos maiorum (; "ancestral custom"Karl-J. Hölkeskamp, Reconstructing the Roman Republic: An Ancient Political Culture and Modern Research (Princeton University Press, 2010), p. 17 online. or "way of the ancestors," plural mores, cf. English "mores"; maiorum is the genitive plural of "greater" or "elder") is the unwritten code from which the ancient Romans derived their social norms. It is the core concept of Roman traditionalism,Mos Maiorum, Brill Online. 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.Hölkeskamp, Reconstructing the Roman Republic, pp. 17–18.
