A Hypothesis

(sciences) Used loosely, a tentative conjecture explaining an observation, phenomenon or scientific problem that can be tested by further observation, investigation and/or experimentation. As a scientific term of art, see the attached quotation. Compare to theory, and quotation given there. Hypothesis - Wikipedia
(general) An assumption taken to be truefor the purpose of argument or investigation.
(grammar) The antecedent of a conditional statement.

Synonyms