Price ceiling: a legal maximum price.
Price floor: a legal minimum price. A minimum wage is a price floor for labor.
Binding: the law stops the market from reaching equilibrium. A ceiling binds only if it is below equilibrium. A floor binds only if it is above.
Shortage: quantity demanded is greater than quantity supplied.
Surplus: quantity supplied is greater than quantity demanded.
Consumer surplus: what buyers are willing to pay minus what they actually pay. The area under demand and above the price.
Producer surplus: what sellers receive minus their cost of supplying. The area above supply and below the price.
Deadweight loss: gains from trades that would help both sides but no longer happen.
Tariff: a tax on imported goods.
Imports: quantity demanded minus quantity supplied at home.
Area of a triangle: ½ × base × height.
Area of a rectangle: base × height.