Webster's Revised Unabridged Dictionary · 1913

Hypothesis

Hypothesis , noun

[New Latin, from Greek {not transcribed} foundation, supposition, from {not transcribed} to place under, {not transcribed} under + {not transcribed} to put. See Hypo-, Thesis.]

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, or to account for a fact or an occurrence; as, the hypothesis that head winds detain an overdue steamer.
An hypothesis being a mere supposition, there are no other limits to hypotheses than those of the human imagination. — J. S. Mill
2.
(Natural Science) A tentative theory or supposition provisionally adopted to explain certain facts, and to guide in the investigation of others; hence, frequently called a working hypothesis.
Collocations (1)
Nebular hypothesis , See under Nebular.