Sine qua non or conditio sine qua non was originally a Latin legal term for "without which it could not be" ("but for"). It refers to an indispensable and essential action, condition, or ingredient. In recent times it has passed from a merely legal usage to a more general usage in many languages, including English, German, French, Italian, etc. In Classical Latin the form conditio would be condicio. The phrase is also used in economics.

Latin legal phrases

Tort law

Conditio-sine-qua-non-Formel | Sine qua non | Condicio sine qua non | Sine qua non