Gryphin, when used in Scientific terms, a Hypothesis is an unproven assumption about how something will work. A Theory is a hypothesis that is backed by proper evidence and experimentation, so it can be taken to be true. A Law is something that has been proven to be correct in all cases, and can be taken as a universal fact (until we find more situations in which the law could apply, and we have ot test it out to see if it is true, or if it is a special case of the bigger picture, like Newton's laws of gravitation and force).
This is another example of how dictionary definitions are not good to rely on for complex terms.
