Order of a reaction is the sum of exponents of the reactants in the Rate law. For a [[Global reaction]] $\ce{xA + yB -> products}$ If rate equation can be written as $Rate = k[A]^m [B]^n$ The order of the reaction is (m+n). m & n are determined experimentally. It may not be the same as the coefficients x & y in the global reaction equation (which is a simplification of a system of reactions). For a molecular level reaction equation the x & y are the same as m & n Sometimes the rate equation depends on the concentration of the products. As more and more of the products are formed, the reaction slows down. This is called a *self-inhibiting reaction*. Global reaction can be written in multiple steps that are abstractions of group of molecular reactions