A term used in an algebra class Bart Simpson takes in the episode "Bart the Genius".
RDRR = Har-de-har-har.
Teacher: So y = r cubed over 3. And if you determine the rate of change in this curve correctly, I think you'll be pleasantly surprised.
The class laughs except for Bart who appears confused.
Teacher: Don't you get it, Bart? Derivative dy = 3 r squared dr over 3, or r squared dr, or r dr r.