plural of ratio decidendi

(law) A standard for judicial review, according to which a law must be rationally related to a legitimate state interest.

(algebra) A theorem which states a constraint on rational solutions of a polynomial equation with integer coefficients.

(social sciences, economics, political science, sociology) A theory that argues individual decisions are based on that individual's understanding of the costs and benefits of a given action, shaped throughout the assumptions of self-interest and rational actors.

The process of economic agents aiming to maximise their objectives, by ensuring the marginal benefit of an action is equal to its marginal cost.