# Definition
The action integral (or simply *action*) is:
$
S = \int L(q^i, \dot{q}^i)\, dt = 0
$
where $q^i$ are the [[generalized coordinates|generalized coordinates]] and $L$ is the [[Lagrangian]]. Minimizing the action $\delta S = 0$ is equivalent to the [[Euler-Lagrange Equations]].