a schedule of how much of an item people will purchase at any particular price of that item during a specified time period, other things constant. The law of demand implies that the demand curve. has a negative slope. When McDonald's runs a special for hamburgers, reducing price of Big Macs.
Shortage exists. when quantity supplied is less than quantity demanded. The law of demand includes the statement "other things being equal.". These other things include all of the following except. the price of that good in the law of demand.