Leverage points are places within a complex system where a relatively small, well-placed intervention can produce a large shift in the system's overall behavior. Donella Meadows organized them into a hierarchy, from shallow leverage points like adjustable parameters and buffers to deep leverage points like the rules, goals, and mindset that generate the system in the first place.

Ludwig von Bertalanffy was an Austrian biologist who founded General Systems Theory, arguing that living organisms are open systems that exchange energy and matter with their environment and maintain themselves through ongoing self-regulation, in contrast to closed, mechanical systems that tend toward equilibrium and decay.

Norbert Wiener was a mathematician who founded the field of cybernetics in the 1940s, defining it as the study of control and communication in the animal and the machine. His work showed that feedback, the process of using information about a system's output to adjust its future behavior, applies equally to a guided missile, a living organism, and a social institution.

Jay Forrester was an American engineer and the founder of system dynamics, the field that models complex systems using stocks, flows, and feedback loops, originally to help industrial companies understand why their operations produced boom-and-bust cycles that no individual manager seemed to be causing on purpose.

Peter Senge is an American systems scientist and author of 'The Fifth Discipline,' the book that brought systems thinking into mainstream management practice by framing it as the fifth and integrating discipline of a learning organization, alongside personal mastery, mental models, shared vision, and team learning.

Donella Meadows was a scientist, writer, and systems thinker best known as lead author of 'The Limits to Growth' and for her widely cited list of 'leverage points,' the places within a complex system where a small shift can produce large changes in behavior, ranked from shallow parameters to deep changes in a system's underlying goals and paradigm.

POSIWID, short for 'The Purpose Of a System Is What It Does,' is a systems thinking heuristic coined by Stafford Beer that judges a system by its actual behavior and outcomes rather than by its stated mission or intentions. If a system reliably produces a certain result, that result should be treated as its real purpose.

Cybernetics is the study of communication, control, and feedback in systems, whether biological, mechanical, or social. It examines how systems regulate themselves toward a goal using information about their own performance, the same principle at work in a thermostat, a steering mechanism, or a well-run team.

Reflexivity describes a situation where observers of a system are also participants in it, so that their beliefs and actions feed back into and change the very system they are observing. Financial markets are a well-known example: investor expectations about prices can influence the prices themselves.

Non-linearity means that a change in a system's input does not produce a proportional change in its output. Small actions can trigger disproportionately large effects, and large efforts can sometimes produce almost no visible change, which breaks the common intuition that outcomes should scale evenly with effort.

Emergent properties are characteristics and behaviors of a system that arise from the interaction of its parts but are not present in, or predictable from, any single part on its own. A traffic jam, a flock of birds turning in unison, and a company's culture are all emergent phenomena.