Pronunciation: (hī-poth'u-sis, hi-),[key] —n., —pl.-sesPronunciation: (-sēz").[key] 1. a proposition, or set of propositions, set forth as an explanation for the occurrence of some specified group of phenomena, either asserted merely as a provisional conjecture to guide investigation (working hypothesis) or accepted as highly probable in the light of established facts.
2. a proposition assumed as a premise in an argument.
3. the antecedent of a conditional proposition.
4. a mere assumption or guess.