Change in demand vs. change in quantity demand

A change in the quantity buyers want to purchase, prompted by any reason other than a change in price (e.g., increase in income, change in tastes), is a change in demand. In graphical terms, it is a shift of the demand curve. If, in contrast the decision to buy more or less is promted by a change in the good's price, then it is a change in quantity demanded, In graphical terms, a change in quantity demanded is a movement along an unchanging demand curve.