rule, regulation / rule, period of ruling / ruler (for measuring length) / period, menstruation

inflection of régler:
/ inflection of régler:

Norma (constellation)

valid, in order (in compliance with the law or the rules)

customary, usual

(figuratively, chiefly in the singular) golden rule (fundamental rule or principle)

(chiefly in the plural) rules of engagement, ROE

as a rule, in general

(mathematics education) rule of three

(chiefly in the plural, figuratively) rule of the game (implied or unspoken principle that governs a facet of behavior, especially one involving strategy)