Rate = k[A]^m[B]^n. Orders m and n are determined experimentally, NOT from stoichiometry (except for elementary reactions). Overall order = m + n. The rate constant k is specific to a reaction at a given temperature. It does NOT depend on concentration. Units of k depend on overall order n: k has units of (mol/L)^(1-n) s^-1. Zero order: mol/(L.s). First order: s^-1. Second order: L/(mol.s). Third order: L^2/(mol^2.s). Higher k means faster reaction. k increases exponentially with temperature (Arrhenius equation). For complex (multi-step) reactions, the rate law is determined by the rate-determining step (slowest step).