The various meanings of legal certainty are examined. The aim is to demonstrate that legal certainty is a principle, in its preponderant normative meaning, in the sense that it establishes a state of affairs that ought to be sought through behavior that contributes to its gradual advancement. This prevalent normative meaning of legal certainty does not exclude the existence of other normative dimensions that perform different efficacy-related functions. Furthermore, the chapter demonstrates that besides being a legal principle, legal certainty can manifest itself as a legislatively established legal rule; a principle recognized by the courts as a rule; a metanorm for the interpretation and application of other norms; or a subjective right resulting from reflexive application of the legal certainty principle itself.