theory - the·o·ry - [thee-uh-ree, theer-ee] - noun, plural the·o·ries.

1. a coherent group of tested general propositions, commonly regarded as correct, that can be used as principles of explanation and prediction for a class of phenomena: Einstein's theory of relativity. Synonyms: principle, law, doctrine.

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7. guess or conjecture: My theory is that he never stops to think words have consequences.

there is a difference!