Medieval term for the subject of a proposition, or that for which the general term in subject position stands. It was medieval doctrine that the general terms in a syllogism stand for things, and are grammatically interchangeable, linked together in a subject-predicate or categorical proposition by the copula. This raises the question of what they each stand for, and what relation has to hold between the things they stand for in order for a sentence to say something true. If it is also supposed that for a sentence to be true the terms must stand for the same thing, then the matter becomes extremely complex, and the doctrine of suppositio eventually embraced distinctions such as formal, material, simple, personal, determinate suppositio and others.