The Pythagorean Theorem, also known as the Pythagorean formula or the Pythagorean equation, is a mathematical concept and formula that states that in a right triangle, the square of the length of the hypotenuse (the side opposite the right angle) is equal to the sum of the squares of the lengths of the other two sides. Some synonymous phrases for the Pythagorean Theorem include the Pythagorean proposition, the Pythagorean principle, and the Pythagorean relationship. Other terms that can be used to describe the concept include the Pythagoras theorem, Pythagoras' theorem, or simply the Pythagorean formula. Regardless of what it's called, the Pythagorean Theorem remains one of the most fundamental concepts in mathematics and has countless real-world applications.