Law of Demand:

The way consumers react to a change in the price of a commodity is so typical that economists state it as a rule of law. This law states that the quantity demanded of a good is inversely (or opposite) related to its price, when we hold constant other factors that influence consumer's consumption of a commodity. An inverse relationship between quantity demanded and price means that quantity demanded will increase if or when price falls and quantity demanded will decline if price rises, all things being equal.