Hypothesis, theory, law are often interchangeable in general use. In their technical senses they are usually discriminated by the scientists and philosophers who employ them.
In general the terms denote an inference from data that is offered as a formula to explain the abstract and general principle that lies behind the data and determines their cause, their method of operation, or their relation to other phenomena.
In such usage hypothesis implies tentativeness in the reference because of insufficient evidence and applies to a well-founded conjecture that serves as a point of departure for scientific discussion or as a tentative guide for further investigation or as the most reasonable explanation of an imperfectly comprehended phenomenon.
Theory, in general use, often means little more than hypothesis or conjecture, but in precise technical use it presupposes more supporting evidence than hypothesis does, a wider range of application, and greater likelihood of truth. It is not always obvious when hypothesis and when theory should be used; in comparable applications hypothesis is preferred by some scientists as the more modest in its claims, theory being preferred by others as suggesting such confidence in the reliability of the inference and its supporting evidence as to imply that it deserves acceptance.
Law ((for fuller treatment see PRINCIPLE )) emphasizes certainty and proof and therefore applies to a statement of an order or relation in phenomena that has been found to be invariable under the same conditions.
However, since such laws are subject to correction or alteration by the discovery of contradictory or additional evidence, the term is often changed in the course of time to theory; thus, what has long been known as Newton’s law of gravitation is currently being revised as a result of Einstein’s discoveries and is sometimes designated as Newton’s mathematical theory of universal gravitation.