Definition of ratio decidendi in US English:

ratio decidendi

Pronunciation /ˌrätēō ˌdesəˈdendē//ˌrāSHēō ˌdesəˈdendī/


  • The rule of law on which a judicial decision is based.

    • ‘If the Court refuses that, there are some interesting arguments about how one determines ratio decidendi.’
    • ‘You must then deal fully with the ratio decidendi of the case, with a detailed analysis of Lord Templeman's judgment on behalf of the majority.’
    • ‘Courts are bound by principles of law, the ratio decidendi of cases.’
    • ‘I do not find it easy to discover the ratio decidendi of Pook's case.’
    • ‘The former are described as being the ratio decidendi (reasons for the decision).’
    • ‘If property suddenly became available all over the country many of the rationes decidendi of the past would be quite inappropriate.’


Latin, literally ‘reason for deciding’.


ratio decidendi

/ˌrätēō ˌdesəˈdendē//ˌrāSHēō ˌdesəˈdendī/