hypothesis

n. explanation which gives a reason for observed phenomena, theory (especially in the sciences); supposition, assumption

A hypothesis (from Greek ) consists either of a suggested explanation for a phenomenon or of a reasoned proposal suggesting a possible correlation between multiple phenomena. The term derives from the  Greek, hypotithenai meaning "to put under" or "to suppose." The scientific method requires that one can test a scientific hypothesis. Scientists generally base such hypotheses on previous observations or on extensions of scientific theories.
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Noun
1. a proposal intended to explain certain facts or observations
(hypernym) proposal
(derivation) speculate, theorize, theorise, conjecture, hypothesize, hypothesise, hypothecate, suppose
2. a tentative theory about the natural world; a concept that is not yet verified but that if true would explain certain facts or phenomena; "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"
(synonym) possibility, theory
(hypernym) concept, conception, construct
(hyponym) model, theoretical account, framework
(part-holonym) theory
(derivation) speculate, theorize, theorise, conjecture, hypothesize, hypothesise, hypothecate, suppose
3. a message expressing an opinion based on incomplete evidence
(synonym) guess, conjecture, supposition, surmise, surmisal, speculation
(hypernym) opinion, view
(hyponym) divination
(derivation) speculate, theorize, theorise, conjecture, hypothesize, hypothesise, hypothecate, suppose

(n.)
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.
  

(n.)
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.
  

A tentative proposal made to explain certain observations or facts that requires further investigation to be verified.