(N/A) General Reaction: $aA + bB \rightarrow cC + dD$
The differential rate expression for the reaction is given by:
Rate $= -\frac{d[R]}{dt} = k[A]^x[B]^y$
Here,the values of $x$ and $y$ are determined experimentally and may or may not be equal to the stoichiometric coefficients $a$ and $b$.
The exponents $x$ and $y$ indicate the sensitivity of the reaction rate to changes in the concentrations of $A$ and $B$ respectively.
$(i)$ $x$ represents the order with respect to reactant $A$.
$(ii)$ $y$ represents the order with respect to reactant $B$.
$(iii)$ $(x + y) = \text{Overall order of the reaction}$.
Order of Reaction: The sum of the powers of the concentrations of the reactants in the rate law expression is called the order of that chemical reaction.
The order of a reaction can be $0, 1, 2, 3$ or even a fraction,and these values are always determined experimentally.