In mathematics and logic, a proposition or statement whose contrapositive is to be derived, or in older philosophy, a thing that is to be converted or transformed.
From Latin 'convertendus,' meaning 'to be converted,' formed from 'convertere' (to turn around, transform) plus the gerundive suffix '-endus' indicating something to be done or changed.
This term reveals how deeply embedded conversion logic is in medieval and classical philosophy—scholars had to name the thing being converted before they could work with it, much like modern programmers name variables before transforming them.
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