# Formula

equation using mathematical or scientific notation

In mathematics and science, a formula is a rule or statement written in algebraic symbols. The plural of formula can be written in two ways: formulae or formulas - the choice is based on personal preference.

Formulas use letters instead of words. A simple example of a formula is y = x. If x=1, the formula y=x would make the statement that x is the same thing as y, therefore, y=1.

In mathematics, a formula can also be an identity which equates two mathematical expressions together. Some key formulas under this category include the Pythagorean theorem, binomial theorem, Euler's formula and De Moivre's formula. The expression "V=lwh", which relates the volume V to the length l, width w and height h of a rectangular box, is another example of a formula in geometry.

In science, one of the most well known formulas is the formula for energy, e = mc2, created by Albert Einstein. Here, e represents energy, m represents mass and c is the speed of light. Thus, energy = mass × speed of light 2.

The formula e = mc2 is also an equation. Every equation is a formula, but not every formula is an equation. For instance, the formula x≡y (x "is defined as" y) is not an equation, because no "=" sign is used.