I don't mean the actual definition of the Euler-Lagrange equation per-se, but rather a word definition that's slipping my mind. I remember that if you want to measure the shortest distance between two points, you have to minimize an integral of all possible paths or something. Is that thing you're minimizing called anything in particular? Basically, I'm trying to remember from my classical mechanics class two years ago on how, when you minimize that thing, you're minimizing something that doesn't physically exist or something to that effect. I realize my description is butchering the whole formalism, but can anyone give me a simple fill in the blank here? You minimize ______ to find the shortest distance between two points.