26.1.1—And use the terms rate equation, order

A rate equation relates rate to concentrations, e.g. rate=k[A]^m[B]^n. m and n are reaction orders, their sum is overall order, and k is the rate constant at a stated temperature.

Half-life is the time for a concentration to halve; the rate-determining step is the slowest elementary step in a mechanism, while an intermediate is formed in one step and consumed in another.

For rate=k[A]²[B], the overall order is three. An intermediate appears in the mechanism but not in the net equation.

Reaction orders are experimental, not automatically stoichiometric coefficients, and the RDS is not always the first step.