Did Aristotle used the term contradiction or the term contradictory in his discussions of reductio ad impossibile?
Two translators who disagree:
For all those which come to a conclusion through an impossibility deduce the falsehood, but prove the original thing from an assumption when something impossible results when its contradiction is supposed (, that is, when the contradictory to the assumption is supposed.) — Aristotle, Prior analytics (translation by Robin Smith)
For all who effect an argument per impossibile infer syllogistically what is false, and prove the original conclusion hypothetically when something impossible results from the assumption of its contradictory — Aristotle, Prior analytics (translation by A.J. Jenkinson, with minor emendations by Daniel Kolak)