level set
subset of a function's domain on which its value is equal
equipotential
region in space consisting of points at the same potential
indifference curve
microeconomic graph; connects points representing different quantities of 2 goods, points between which a consumer is indifferent: i.e. the consumer doesn't prefer one combination or bundle of goods over another combination on the same curve
isoline
curve joining points with equal value on a 2D graphic representation
contour line
line on a map connecting points of equal elevation