Indifference curve

Definition

Consider two goods $A$ and $B$, with a graph whose axes plot quantities of $A$ and $B$. Consider an individual or household consumer. Any point in the graph corresponds to the choice of a quantity of $A$ consumed (the $A$-quantity coordinate) and a quantity of $B$ consumed (the $B$-quantity coordinate).

An indifference curve for this consumer between the two goods is a curve representing a set of points such that the consumer is indifferent between the consumption possibilities for each point. In other words, choosing the quantity of consumption for each good corresponding to one point on the indifference curve gives the consumer the same utility as choosing another point.

Equivalently, indifference curves can be thought of as level sets for the consumer's utility function.