A causal loop diagram is a visual map of a system that shows the variables involved and the causal links between them, marked with polarities that show whether one variable increases or decreases another, and grouped into the reinforcing and balancing loops that drive the system's overall behavior.

VUCA is an acronym for Volatility, Uncertainty, Complexity, and Ambiguity, originally coined by the U.S. Army War College to describe the operating conditions leaders increasingly face, where change is rapid, causes and effects are unclear, many interacting variables are at play, and information is open to multiple interpretations.

System archetypes are recurring structures of feedback loops that show up again and again across very different systems and produce familiar, often frustrating patterns of behavior, such as 'Fixes That Fail,' where a quick fix relieves a symptom but worsens the underlying problem over time, or 'Tragedy of the Commons,' where individually rational choices deplete a shared resource.

Autopoiesis, a term coined by biologists Humberto Maturana and Francisco Varela, describes a system that continuously produces and maintains the very components and processes that make it what it is, effectively regenerating itself from the inside rather than being assembled and maintained by an outside designer.

Holism is the principle that a system must be understood as a whole, because its properties and behavior cannot be fully predicted by examining its parts separately. The classic systems thinking phrase for this is that the whole is greater than, and often qualitatively different from, the sum of its parts.

Sustainability challenges, from resource depletion to climate change to biodiversity loss, are quintessential systems problems because they involve long delays between cause and effect, feedback loops that cross ecological and economic boundaries, and stakeholders whose incentives often point in different directions.

A learning organization is one that continuously expands its capacity to create the results it truly wants, by treating learning as a core, ongoing activity rather than a one-off training event. Peter Senge popularized the term through five disciplines: personal mastery, mental models, shared vision, team learning, and systems thinking.

Personal mastery is another of Peter Senge's five disciplines, describing an individual's ongoing practice of clarifying what truly matters to them and continually developing the skill and patience to close the gap between that personal vision and their current reality, rather than settling for good enough.

Boundary critique is a systems thinking practice that asks, deliberately and repeatedly, what has been included in and excluded from the definition of a problem or a project, and who decided where that boundary should sit. Every system definition is a choice, and that choice determines whose interests count.

Mental models are the deeply held, often unexamined assumptions, generalizations, and images that shape how a person understands the world and makes decisions. Two people can look at the same data and reach opposite conclusions because their underlying mental models about how the system works are different.

General Systems Theory, developed by biologist Ludwig von Bertalanffy, proposes that systems across very different domains, biological, mechanical, social, and ecological, share common organizing principles, such as hierarchy, openness to the environment, and self-regulation, that can be studied as a unified field rather than domain by domain.