[This is part of the series: The Complete Guide To Economics 101.]
What is the marginal rate of substitution?
The Marginal Rate Of Substitution is the rate where a person is willing to trade one good or service for another good or service.
Formally, this is movement, along an indifference curve.
More technically, the marginal rate of substitution is the slope of an indifference curve at any given point.
And then, everyone wants to start talking about calculus.