What is reaction order and how is it determined?

Reaction order is the exponent to which reactant concentration is raised in the rate law: rate = k*CA^n*CB^m. Order with respect to A is n, with respect to B is m, and overall order is (n+m). It is determined experimentally by: method of initial rates (varying one concentration), integral method (fitting concentration-time data), or half-life method. Order can be zero, fractional, or negative for complex mechanisms, and does not necessarily equal stoichiometric coefficients.