The economic principle that higher prices generally reduce the quantity consumers demand, other things equal, is the law of demand.
The law describes movement along a demand curve when the good’s own price changes while relevant conditions remain constant. At a lower price, consumers usually buy more; at a higher price, they usually buy less. The response can reflect substitution toward alternatives and the effect of the price on a buyer’s real purchasing power.
The phrase “other things equal,” or ceteris paribus, matters. Income, tastes, expectations, population, and the prices of related goods can shift the entire demand curve. A higher price can occasionally coincide with higher demand for unusual goods, such as prestige products, but those cases do not overturn the standard principle.
The law of demand concerns quantity demanded, not demand itself. Economists reserve “a change in quantity demanded” for a price-driven movement along the curve and “a change in demand” for a shift caused by another factor.