The law of supply describes the relationship between the price of a good and the quantity supplied by producers. When the price of a product rises, the quantity supplied by producers increases, and when the price falls, the quantity supplied decreases. This principle operates under the ceteris paribus assumption, meaning all other factors, such as input costs, technology, future expectations, and the number of sellers, are held constant.

The rationale behind the law of supply lies in the profit motive of producers. Higher prices offer the potentia; to supply more of the good or service. Conversely, producers may scale back their production when prices decrease to avoid losses.

This relationship is depicted by the upward-sloping supply curve. Movement along the supply curve occurs when there is a change in the price of the product while other factors remain constant. If the price increases, producers move along the curve to supply a higher quantity. If the price decreases, they move to supply a lower quantity. This demonstrates the direct relationship between price and quantity supplied.