Ratio Decidendi
/RAY-shee-oh deh-SID-en-dee/
The reason for the decision — the binding legal principle or rule that forms the basis of a court's judgment.
Full Definition
Ratio decidendi (Latin: 'reason for deciding') is the specific legal rule or principle of law that was essential to the court's decision in a case. It is the binding part of a precedent — the proposition of law for which the case stands authority. Distinguished from obiter dicta (things said in passing, which are merely persuasive). Identifying the ratio can be difficult: multiple judges may decide the same case for different reasons, each judge's ratio may differ, and the ratio must be extracted from the facts and ruling together.
In Indian Law
Under Article 141 of the Constitution, it is the ratio decidendi — not the entire judgment — that is binding. The Supreme Court in Quinn v. Leathem principle (applied in Indian courts) states: 'A decision is only an authority for what it actually decides.' Indian courts regularly distinguish cases on facts rather than openly overruling them, creating a nuanced body of precedent.