A result that has been proved to be true (using facts that were already known).
Example: The "Pythagoras Theorem" proved that for a right angled triangle a2 + b2 = c2
A Theorem is a major result (if it is just a minor result it is called a "Lemma")
* Intermediate Value Theorem
* Binomial Theorem
* Fundamental Theorem of Arithmetic
* Fundamental Theorem of Algebra
See: Pythagoras Theorem