Hypothesis and theory are two different, and common terms that are usually used in science. They usually describe the scientific process of a particular phenomenon. In the case of a hypothesis, it is usually referred to as a guess, a sort of observation that is being made when a scientific process is still going on.
Hypothesis, in science, refers to a scientific process that is still undergoing investigation, and it can be accepted or rejected. The hypothesis is usually a stage before theory. On the other hand, theory can be described as a scientific process that deals with nature, explanation of occurrences.
While the hypothesis is being made when practical is still going on, theories are drawn out from the observation of an occurrence. A theory can only be validated by the observation of an existing phenomenon. As a matter of fact, a hypothesis can also be made based on some theories that might have been made after an observation.