My basic knowledge of these two words is that they both mean the same thing. So why are they used differently, and what is their difference in meaning?

  • 3
    While in common vernacular today, "hypothesis" and "theory" often are used to refer to the same or very similar concepts, they actually have very different meanings - especially in the scientific community. Hopefully, someone can come in and explain the difference between "hypothesis", "theory", and "law" from a scientific standpoint.
    – Iszi
    May 10, 2011 at 2:29
  • See also this related question Jul 5, 2011 at 12:55

5 Answers 5


Let's get some standard definitions in here.


A proposal intended to explain certain facts or observations; a tentative insight into the natural world; a concept that is not yet verified but that if true would explain certain facts or phenomena.

A scientific hypothesis that survives experimental testing becomes a scientific theory.


A well-substantiated explanation of some aspect of the natural world; an organized system of accepted knowledge that applies in a variety of circumstances to explain a specific set of phenomena.

Theories can incorporate facts and laws and tested hypotheses.

All from wordnetweb.princeton.edu/perl/webwn.

  • 1
    @Mathew both of them are loan - words from Greek Language. If you may analysed them then you will come to the same conclusion. Thus your approach is the most accurate of all , according to my opinion. Also the word "phenomena" is a loan - word May 10, 2011 at 8:05

A hypothesis is a testable prediction.

A theory is a tested, and usually widely accepted, hypothesis.


I think this is mainly related to their usage in american-english. Originally, these two words have very different meanings.

A hypothesis is an assumption made for the sake of argument.

Theory is the analysis of a set of facts in their relation to one another used to draw a conclusion or an explanation of some phenomenon. A theory may use a number of hypothesis to draw one, or more, conclusions.

Unfortunately, people often say "it's just a theory" almost as if theory was an assumption about something. Nonetheless, you can see the difference from the definitions above.


A hypothesis is something expected to be true, but not yet proved (Synonyms: presumption, assumption, conjecture). For example:

  • The Continuum Hypothesis: There are more real numbers than integers.
  • The Collatz Conjecture: If a number is even, find n/2; if it is odd, find 3n + 1. Upon repeating, one will reach the number 1 eventually.

However, a theory is a proposition which is most likely to be true, and is derived from other true statements (theorems). They may also be analyses of facts. For example:

  • Game theory: A topic in economics based on real-life strategies.
  • Set theory: A branch of mathematics focusing on sets, both in real life and theoretical.

Hypothesis is a single statement regarding relationship between variables that can be tested by observation. Hypotheses are usually formulated to support or deny theories. Usually, several hypotheses on a fact, if scientifically proven, become a theory.

A theory, on the other hand, is a systematic set of generalization that explains some phenomenal linking variables in order to come up with principles that are internally consistent. It should be noted that a theory is only accepted after successful researches on a certain formulation about a fact are done while a hypothesis is just a mere formulation of a fact.

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