n. 1. a presupposition, especially a restriction on the domain, that is indispensable to the proof of a theorem and stated as part of it; a restriction on the truth of the stated result, so that the latter only holds if the stated precondition is satisfied. 2. (Logic) a statement related to another by implication; it is either a necessary condition if its truth is required for the truth of another, or a sufficient condition if its truth guarantees that of the other. 3. (Statistics) short for experimental condition (sense 1).