Answer: Hypothesis, experiment
Explanation: When scientists set up a hypothesis, which is an assumption that needs to be proven by an experiment, they conduct an experiment based on starting assumptions. If the experiment shows that the hypothesis is incorrect, then they have to revise the hypothesis. On the basis of the revised hypothesis, scientists are setting a new experiment to prove the new hypothesis as true. So hypotheses are revised and new experiments are put in place until an experiment proving the revised hypothesis as accurate, which is no longer a hypothesis, can be considered as scientific theory. Everything that is empirically proven through an experiment is considered true.