DEFINITION OF A HYPOTHESIS · Hypothesis A tentative explanation that accounts for facts and can be tested by further investigation; a theory Something taken to be true for the purpose of argument or investigation; an assumption .EXperiment A test under controlled conditions that is made to demonstrate a known truth, examine the validity of a hypothesis, or determine the efficacy of something previously untried American Heritage dictionary, 3rd Edition2 DEFINITION OF A HYPOTHESIS • Hypothesis A tentative explanation that accounts for facts and can be tested by further investigation; a theory Something taken to be true for the purpose of argument or investigation; an assumption •Experiment A test under controlled conditions that is made to demonstrate a known truth, examine the validity of a hypothesis, or determine the efficacy of something previously untried. American Heritage Dictionary, 3rd Edition