In science, a hypothesis is an idea about how or why something works that must be carefully tested in order to verify whether it is true or false. To test a hypothesis, a scientist must follow scientific method so that the hypothesis can be verified or refuted by other scientists.
A hypothesis is an educated guess based on previous observations. However, an important element of a hypothesis is that it has not yet been accepted as fact by the scientific community. For this reason, a hypothesis is either verifiable or falsifiable, meaning it requires evidence acquired through testing to be accepted as fact.