"Supposure" is a word in ENGLISH

By the hypothesis; upon the supposition; upon the theory or facts assumed

A supposition; a proposition or principle which is supposed or taken for granted, in order to draw a conclusion or …

A tentative theory or supposition provisionally adopted to explain certain facts, and to guide in the investigation of others; hence, …

A supposition, assumption, or theory; a theory set up by the pros-ecution, on a criminal trial, or by the de-fense, …

That which is supposed; hypothesis; conjecture; surmise; opinion or belief without sufficient evidence.

Including or implying supposition, or hypothesis; supposed.

An affirmation, or distinction from a supposition or hypothesis.