Conley's fundamental theorem of dynamical systems
Conley's fundamental theorem of dynamical systems or Conley's decomposition theorem states that every flow of a dynamical system with compact phase portrait admits a decomposition into a chain-recurrent part and a gradient-like flow part. Due to the concise yet complete description of many dynamical systems, Conley's theorem is also known as the fundamental theorem of dynamical systems.
Source: Wikipedia — Conley's fundamental theorem of dynamical systems (CC BY-SA 4.0)