Glossary

The words used across these essays, in plain language. Each term is defined once, here, and used the same way everywhere else on the site.

Above the ladder: The judgment about which level a situation needs and why. Four parts: frame selection, purpose, learning how you learn, and return to the tangible. Explained in Which Lens, and When.
Abstract thinking: Pulling out what several tangible cases share, and deciding which differences do not matter for your purpose. A lossy compression. Explained in Ten Cups, One Word.
Abstraction: A compression that keeps what matters for a purpose and drops the rest. Every category, model, diagram and rule is an abstraction. Explained in Ten Cups, One Word.
Abstraction ceiling: The point past which more abstraction stops revealing things and starts hiding them, without any obvious sign that you have passed it. Explained in Stuck at a Good Level.
Attention: The resource being traded. A phone system is built to get more of it, which is why the design is the same whichever app you are looking at. Explained in The Phone in Your Pocket.
Balancing loop: A feedback loop with a minus sign, which pushes back toward a target and settles there. Explained in The Shower Tap and the Thermostat.
Bottleneck: The part of a system that limits its output. Improving anything else changes nothing, however much effort goes into it. Explained in The Queue Is Not the People.
Boundary: The edge of a system, and therefore a decision. Where you draw it decides what you can see and what you can influence. Explained in The Queue Is Not the People.
Category: A set of things grouped by what can be ignored. A category is a decision about differences, not a discovery about the world. Explained in Ten Cups, One Word.
Compression: Turning many particulars into one general. It buys reach and costs resolution, and the exchange is usually a good one. Explained in Ten Cups, One Word.
Constraint: Any feature that reduces the space of possible things. A constraint does not limit the work, it decides what the work is. Explained in The Form Makes the Poem.
Contour drawing: Drawing an edge in one continuous line without lifting the pen, which narrows attention to the boundary between things. Explained in Drawing What You See.
Defamiliarization: Deliberately making an ordinary thing strange so that it can be seen again. Explained in Making the Stone Stony.
Delay: The time between an action and its effect. A delay is a parameter, not a fault, and it decides whether a loop settles or hunts. Explained in The Shower Tap and the Thermostat.
Desired path: A track worn into grass by people going where the paving did not allow. It is a report on the design, written in the ground. Explained in The Path Across the Grass.
Dogma: A principle whose cases have been removed so that it can never be checked. It is obedience with the evidence deleted. Explained in Rules That Travel.
Emergence: Behavior that belongs to the arrangement and cannot be located in any part of it. Explained in Wholes No Part Contains.
Empty space: The interval between things, which is a shape in its own right and is often where the meaning of a work or a conversation sits. Explained in The Meaning of Empty Space.
Fast variable: A variable that moves quickly relative to the time you are watching. It moves a great deal and decides very little. Explained in Fast Variables, Slow Variables.
Feedback: An output that returns as an input. The basic unit of a loop, and the reason some patterns repeat. Explained in The Shower Tap and the Thermostat.
First-order consequence: Another effect of the same action, at the same kind of level. Usually predictable, and usually the answer you already had. Explained in Then What?.
Flow: A rate of change into or out of a stock. The level of a stock tells you almost nothing without the flows behind it. Explained in The Queue Is Not the People.
Frame (lens): A way of looking that makes some things visible and hides others. Every frame is a trade, and the trade is rarely stated. Explained in Which Lens, and When.
Goal: What you want. A system is indifferent to it, and a measure stands in for it, and the standing-in can go wrong. Explained in Perfectly Optimized, Pointless.
Goodhart's law: When a measure becomes a target it ceases to be a good measure. Named after Charles Goodhart, and usually quoted in a paraphrase. Explained in Perfectly Optimized, Pointless.
Habituation: The reduction of attention to something repeated. The mechanism that makes the ordinary efficient and invisible at the same time. Explained in Making the Stone Stony.
Heuristic: A rule of thumb, used because it is usually right and cheap, not because it is always right. Explained in Rules That Travel.
Information loss: What a compression leaves out. Sometimes harmless, sometimes the entire answer, and always invisible from inside the compression. Explained in Ten Cups, One Word.
Law: A rule with an enforcement mechanism behind it. If you do not know who enforces it, you do not know how seriously to take it. Explained in Rules That Travel.
Levels of learning: A scheme for how much a learner has changed: from correcting a response, to changing the set of responses, to changing the frame that picks them. Explained in Learning to Learn to Change.
Local rule: A rule applied by each part separately, which together produce a whole nobody designed. Explained in Wholes No Part Contains.
Loop thinking: Adding time to a system view: outputs return as inputs. Reinforcing loops amplify, balancing loops seek a target, and delays cause overshoot and oscillation. Explained in The Shower Tap and the Thermostat.
Map and territory: The claim that a model is a distortion made on purpose, and that knowing its omissions is what lets you use it without being used by it. Explained in The Map Is Not the Territory.
Measure: A number chosen to stand for a goal. It is a compression, and every compression has a shape. Explained in Perfectly Optimized, Pointless.
Metaphor: A description borrowed from another place, which brings the distortions of that place with it. Useful up to the point where it breaks. Explained in Every Metaphor Is a Borrowed Map.
Model: A description built to answer a question, defined by what it leaves out rather than by what it includes. Explained in The Map Is Not the Territory.
Negative space: The shape of the empty area between marks. In a drawing it often carries more of the form than the marks do. Explained in Drawing What You See.
Nominalisation: Turning a process into a noun, and so deleting the verb that said who was doing it. Explained in The Noun That Froze a River.
Polarity: The plus or minus sign on a feedback loop. It says which way the loop pushes when you leave it alone. Explained in The Shower Tap and the Thermostat.
Principle thinking: A general rule or value that tells you what to do or expect in cases you have not met. An abstraction given authority over action. It has scope and exceptions. Explained in Rules That Travel.
Purpose: What the thinking is for, and whom it serves. A stated purpose and an actual purpose can differ, and only one of them is doing the work. Explained in Perfectly Optimized, Pointless.
Reification: Treating an abstraction as if it were the concrete thing. The grade is not the learning, and the diagram is not the system. Explained in Ten Cups, One Word.
Reinforcing loop: A feedback loop with a plus sign, which amplifies and runs away in one direction. It does not care which direction. Explained in The Shower Tap and the Thermostat.
Rule: A decision about what to do, made in advance, by somebody with the standing to make it. A rule is usually about a recurring situation and is usually local. Explained in Rules That Travel.
Scope: The set of cases a rule was made for. It is the part of a principle that is not in the principle. Explained in Rules That Travel.
Second-order consequence: An effect that acts on the arrangement rather than on the thing. It is usually where the cost and the cause are hiding. Explained in Then What?.
Slow variable: A variable that moves slowly relative to the time you are watching. It moves a little and decides nearly everything. Explained in Fast Variables, Slow Variables.
Stock: A quantity that has accumulated: people waiting, money owed, water in a tank. Its level depends on the difference between flows. Explained in The Queue Is Not the People.
System thinking: Explaining behavior by structure: parts, relationships, stocks, flows, constraints, boundaries. The same parts in a different structure behave differently. Explained in The Queue Is Not the People.
Tangible thinking: Attention on one specific thing or event, the kind you can point at. High-resolution, not primitive. Explained in The Cup on the Table.
Test of a lens: Whether a way of thinking changes a decision, a prediction, or a cost. If it changes none of the three, it is not being used to decide anything. Explained in Does It Change What You Do?.