Can you think of more examples from each category You must be knowing that speed of an automobile is expressed in
terms of change in the position or distance covered by it in a certain
period of time Similarly, the speed of  a reaction or  the rate of a
reaction can be defined as the change in concentration of  a reactant
or product in unit time To be more specific, it can be expressed in
terms of:
(i) the rate of decrease in concentration of any one of the
reactants, or
(ii) the rate of increase in concentration of any one of the products