Given the task definition and input, reply with output. In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

Lisi defined a "universal reservoir" for a quantum mechanical analogue of this quantity, which can be produced by Wick rotations on a Feynman path integral. One principle describing this quantity can be unified with the maximum entropy principle since path uncertainty can be measured by the Shannon information. General relativity uses the Einstein-Hilbert type of this quantity which yields the Einstein field equations, and the shape of the trajectory of this quantity over two specific endpoints is determined through Maupertuis' principle. The Euler-Lagrange equation for this quantity of a system yields the evolution of a classical system, and the functional derivative of this quantity with respect to generalized coordinates goes to zero in accordance with Hamilton's principle. For 10 points, identify this quantity which is defined as the time integral over a given path of the Lagrangian of a system, and is symbolizes S.
Science