sine qua non

[Latin, Without which not.] A description of a requisite or condition that is indispensable.

In the law of torts, a causal connection exists between a particular act and an injury when the injury would not have arisen but for the act. This is known as the but for rule or sine qua non rule.

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sine qua non (see-nay kwah nahn) prep. Latin for "without which it could not be," an indispensable action or condition. Example: if Charlie Careless had not left the keys in the ignition, his 10-year-old son could not have started the car and backed it over Polly Playmate. So Charlie's act was the sine qua non of the injury to Playmate.

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sine qua non noun absolute condition, absolute prerequisite, antecedent, condition, contingency, essential clause, essential condition, essential matter, essential part, essential qualification, indispensable condition, indispensaale item, necessity, precondition, prerequisite, prime conntituent, prime ingredient, qualification, requirement, vital concern

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See also: center, cornerstone, essence