Mathematics
The Epsilon-Delta Definition of a Limit Explained
Quick fact
The epsilon-delta definition was largely refined in the 19th century, most notably by the mathematician Karl Weierstrass, to eliminate inconsistencies in early calculus that relied on 'infinitesimals.'
Why this is interesting
You've probably learned that a limit is the value a function 'gets closer and closer to.' But did you know that mathematicians, to make this truly precise, use a challenge game involving the Greek letters epsilon and delta?