Law: A descriptive generalization about how some aspect of the natural world behaves under stated circumstances.
Hypothesis: A testable statement about the natural world that can be used to build more complex inferences and explanations.
Theory: In science, a well-substantiated explanation of some aspect of the natural world that can incorporate facts, laws, inferences, and tested hypotheses.
(Source: http://arstechnica.com/science/2006/08/5164/)
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How it works...
"Massive objects are attracted to each other by the force of gravity." == Scientific Fact.
"Objects in motion remain in motion. For every force there is an equal an opposite reaction. Force is mass times acceleration." == Scientific Law (Newton's Laws of Motion).
"The bending of space under the influence of gravity can cause light to curve around massive objects." == Scientific Hypothesis (Verified by Eddington's 1919 solar eclipse observations).
All of the above (and a whole lot more) put together == General Theory of Relativity.