hypothesis

(noun) a proposal intended to explain certain facts or observations.

(noun) a tentative insight into the natural world; a concept that is not yet verified but that if true would explain certain facts or phenomena. Synonyms: possibility, theory. Examples: "A scientific hypothesis that survives experimental testing becomes a scientific theory." "He proposed a fresh theory of alkalis that later was accepted in chemical practices."

(noun) a message expressing an opinion based on incomplete evidence. Synonyms: guess, conjecture, supposition, surmise, surmisal, speculation.