The word "equation" is related to the word "equals" and generally describes a state of balance or equilibrium, according to Dictionary.com. Equations are commonly used in mathematics and chemistry.
A mathematical equation is a statement that asserts that two different expressions are equal. The expressions are usually separated by an equals sign to show that one side balances the other.
A chemical equation is a formula for showing a chemical reaction. It displays the type and the amount of starting materials and the results that are produced when they react. The inputs must equal the outputs, as nothing in the reaction is wasted.