Emily Dickinson Lexicon

HY-POTH'E-SIS, n. [L. from Gr. ὑποθεσις, a supposition; υποτιθημι, to suppose; υπο and τιθημι.]

1. A supposition; a proposition or principle which is supposed or taken for granted, in order to draw a conclusion or inference for proof of the point in question; something not proved, but assumed for the purpose of argument. Encyc.
2. A system or theory imagined or assumed to account for what is not understood. Encyc.