The order of a chemical reaction has specific characteristics defined in the NCERT text:

1. Definition: It is defined as the sum of powers of the concentration of the reactants in the rate law expression .
2. Experimental determination: The order is an experimental quantity and cannot be predicted merely by looking at the stoichiometric coefficients of the balanced chemical equation .
3. Values: Unlike molecularity, which is always an integer, the order of a reaction can be 0, 1, 2, 3, and even a fraction . Therefore, the statement that it is 'always a whole number' is incorrect.