Overall Order
The sum of the individual orders with respect to every reactant appearing in the rate law.
Formula / equation
n = m₁ + m₂ + …
Unit
Dimensionless
In depth
Overall order determines the mathematical form of the integrated rate law, the units of the rate constant and the shape of the concentration–time curve. It is a purely empirical description of how the rate responds to dilution, not a statement about the reaction mechanism.
Examples in the real world
rate = k[H₂][I₂] is second order overall; rate = k[NO]²[O₂] is third order overall.