A change in demand means that the entire demand curve shifts either left or right. A change in quantity demanded refers to a movement along the demand curve, which is caused only by a chance in price. ... In this case, the demand curve doesn't move; rather, we move along the existing demand curve.
Change in quantity demanded refers to change in the quantity purchased due to increase or decrease in the price of a product. ... On the other hand, change in demand refers to increase or decrease in demand of a product due to various determinants of demand, while keeping price at constant.
