Change in demand:

change in quantity demanded occurs when the consumption of a commodity increases or decreases as a result a change in the price of the commodity, when all other demand factors remain unchanged. This is shown as a movement along the same demand curve.

There are two types of changes in quantity demanded: an increase in quantity demanded and a decrease in quantity demanded. A change in demand, on the other hand, occurs when either more or less quantity of a commodity is now demanded when the own price of the commodity has not changed. A change in demand is normally occurs when there is a change in any of the other demand factors (referred to as demand shifters). It causes a complete shift in demand curve.