+The **Action Principle** reveals that a system's evolution, from planets to particles, follows a path that minimizes or extremizes a quantity known as the [Action](/wiki/Action). This profound and unifying idea, central to [Field Theory](/wiki/Field_Theory) and beyond, frames the laws of the universe with elegant mathematical beauty.
+## See also
+- [Lagrangian](/wiki/Lagrangian)
+- [Hamiltonian](/wiki/Hamiltonian)
+- [Calculus of Variations](/wiki/Calculus_of_Variations)
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