Every term, in one line

No piece on this site uses a term without defining it. These are the definitions.

Most of these are also the blocks in Focus, a game where you learn them by knocking them down.

A/B test

Running two versions at once to see which is better, on real people. L6

advanced packaging

The step that stitches a processor and its memory onto one piece. Was the bottleneck until memory took over. L2

agent

A model that takes actions on its own, in steps, rather than just answering. It uses tools and keeps going. L6

Air permit

A cap on what the site is allowed to emit. It is what makes gas complicated. L1

Allocation

Being told how much you may buy rather than buying what you want. What shortage feels like. L2

annualised

The most recent month multiplied by twelve. A real measure, presented flatteringly. Ask which month. Band

Attention

The mechanism that decides what the model looks at. Also the thing that makes long context expensive. L4

Availability zone

One failure domain inside a region. Lose one and the design is supposed to survive. L3

backlog

Work a company has signed contracts for but not yet delivered or been paid for. Band

basis points

Hundredths of a percentage point. 100 basis points is one percent. Used because small moves matter in credit. Band

Batching

Serving many requests together. Cheaper per request, worse for whoever is waiting. L5

Behind the meter

Generating power on site so you never touch the public grid, or the queue in front of it. L1

benchmark

A standard test used to compare models. Useful, and easy to lean on harder than it deserves. L4

Binning

Sorting chips by how fast they turned out. The slow ones become cheaper products. L2

Canary

Shipping to a few users first so a failure is small. L6

Capacity block

Compute rented in fixed chunks for a fixed window. A common way to buy compute for training. L3

capex

Capital expenditure. Money spent on things you keep, like buildings and chips, rather than on running costs. Band

Checkpoint

A saved copy of the model mid-run. Lose them and you restart weeks of work. L4

Circular deal

An investment that comes back as revenue. Real money, and it counts twice in the story. Band

Class action

One case brought on behalf of many. Turns a small claim into an existential one. Band

Closed loop

Recirculating the same water instead of drinking more. Uses far more electricity to do it. L1

Colocation

Renting space in someone else's building for your own machines. L3

Compliance deadline

The date an obligation becomes real. Almost always later than written, and never optional. Band

Consumption

Water that evaporates and does not come back, as opposed to water borrowed and returned. L1

context window

How much text a model can hold in mind at once. Bigger means it can read a longer document before answering. L4

Cooling tower

Where the heat finally leaves the site, carried away by evaporating water. L1

Covenant

A condition in a loan. Break it and the lender can demand the money back immediately. Band

CoWoS

The packaging step that bonds chip and memory together. One vendor, one bottleneck. L2

credit default swap

Insurance against a company failing to repay. The price of it is the market's view of how risky that company is. Band

Credit spread

The extra interest a borrower pays over a safe rate. The market pricing your risk. Band

Curtailment order

The grid telling a large load to switch off. Increasingly the price of connecting at all. L1

Damages

What losing a case costs in money. Band

Data centre ban

A local prohibition on building. Cheap to pass, and it lasts. Band

Depreciation

Spreading a chip purchase across its useful life. Shorten the life and profits fall. Band

Discovery

The phase where each side has to hand over documents. Where the interesting things surface. Band

Distillation

Teaching a small model to imitate a large one. Many cheaper models are made this way. L4

Double ordering

The same buyer ordering from two suppliers to be safe, which makes demand look bigger than it is. L2

Drift

The world changing under a model that did not change with it. L6

Easement

The legal right to run cable across land you do not own. L1

Emissions cap

The hard ceiling on the air permit. Exceed it and the site stops. L1

Eval

A test of what a model can do. Whoever writes the eval decides what counts as progress. L4

Evaporative cooling

Cooling by letting water evaporate. Cheap on power, expensive on water. L1

Export controls

Rules on which chips can be sold where. Redrawn faster than anyone can plan around. Band

Fair use

The defence that training on copyrighted work is permitted. Unsettled and worth billions. Band

Feeder

The line that carries power the last stretch into the site. L1

Firm power

Power guaranteed to be there. Costs far more than power that is usually there. L1

foundry

A factory that manufactures chips designed by somebody else. TSMC is the one that matters. L2

frontier model

The most capable model a lab currently sells. L4

Frozen wellhead

In a freeze, gas wells ice up. The fuel fails exactly when demand peaks. L1

gigawatt

A billion watts. Roughly the output of one large power station, or the demand of about 750,000 homes. L1

GPAI

General-purpose AI. The EU AI Act's category for models that can do many different tasks, which carries its own obligations. Band

gross margin

What is left of each sale after the cost of making the thing, before wages and everything else. Band

Guardrail

A check that sits around the model and blocks output it should not produce. L6

Hallucination

A confident answer that is not true. The reason evals exist. L6

HBM

High-bandwidth memory. Stacked memory sitting beside the processor, feeding it data fast enough to keep it working. L2

high-bandwidth memory

Memory stacked right next to a processor so it can be fed fast enough to stay busy. The scarce part of a chip in 2026. L2

Hoarding

Buying more than you need because you are afraid you will not get more later. L2

Hot aisle

The side of the rack the heat comes out of. Get the airflow wrong and nothing runs. L3

Human in the loop

A person approving the step that cannot be undone. L6

hyperscaler

One of the handful of companies large enough to build data centres at global scale: Amazon, Microsoft, Google, Meta. L3

Impairment

Admitting an asset is worth less than you paid. It hits profit all at once. Band

Incident

The half hour where everyone finds out what the system really does. L6

inference

Running a trained model to get an answer. The electricity bill of using AI, as opposed to building it. L5

Injunction

A court order to stop, now. The one thing in this layer that moves faster than a build. Band

Interconnect

The wiring that lets many chips act like one. Often the real limit on a big run. L3

interconnection queue

The waiting list to get plugged into the electricity grid. In busy regions it runs for years. L1

Interposer

The silicon bridge that carries signals between the processor and its memory stack. L2

Islanding

Running disconnected from the grid on your own generation. L1

KV cache

Memory that saves the model re-reading the conversation each token. Where serving cost hides. L5

Lead time

How long between ordering and receiving. The number that quietly sets everyone else's plans. L2

Liquid cooling

Cooling with fluid instead of air, because air stopped being enough. L3

Local hearing

The public meeting where the project is actually decided. L1

Long context

Feeding a model far more at once. Capability that scales cost faster than usefulness. L4

MCP

Model Context Protocol. The shared standard for how an agent connects to tools and data. L5

megawatt

A million watts. A thousandth of a gigawatt, and roughly the draw of a small data centre hall. L1

Microgrid

A small self-contained grid with its own generation and controls. L1

Mixture of experts

Only part of the model runs for any request. Cheaper to serve, harder to fit in memory. L4

Model Context Protocol

The shared standard for how an agent talks to tools and data. Think of it as a plug shape everyone agreed on. L5

Moratorium

A temporary local ban on new data centres, usually while rules are written. L1

neocloud

A newer company that rents out AI chips by the hour, competing with the big clouds on price and speed. L3

Node

The manufacturing generation, like 3nm. Smaller means faster, hotter and far more expensive. L2

Noise limit

A decibel cap at the fence line. Cooling fans are the reason it matters. L1

Observability

Being able to see what the system did. The difference between debugging and guessing. L5

Off-balance sheet

Debt held somewhere that does not show up on the parent company accounts. Band

open-weight

A model whose internals are published, so anyone can run it on their own machines rather than renting it. L4

Option agreement

A right to buy the land later. Cheap to hold, and how almost every site starts. L1

Orchestration

Deciding which step runs when, and what happens when one fails. L5

Oversubscription

Selling more capacity than exists, on the bet that not everyone shows up at once. L3

Peaker pad

Where the fast-start gas turbines sit. Expensive power, available in minutes. L1

Post-training

The shorter phase that turns a raw model into something usable and safe. L4

PPA

A long contract to buy power at a set price. How most clean power gets financed. L1

pre-leased

Rented before it is finished. When most space is pre-leased, supply is not meeting demand. L3

Pretraining

The long first run where a model learns from a huge pile of text. Where the money goes. L4

PUE

Power used by the whole building divided by power used by the computers. 1.0 is perfect. L3

Quantisation

Storing the model at lower precision. Smaller and faster, and slightly worse. L4

Rack

The cabinet the accelerators live in. Power and cooling are budgeted per rack, not per chip. L3

RAG

Fetching documents and handing them to the model so it answers from sources, not memory. L5

Rate limit

The cap on how much you can ask for. What capacity scarcity feels like from outside. L5

Refinancing

Replacing old debt with new. Fine until rates move. Band

Region

A cluster of sites treated as one place. Where your data legally lives. L3

Reserve margin

Spare generation above expected peak. The number that decides if the lights stay on. L1

Retrieval

Pulling relevant documents in before answering, instead of hoping the model memorised them. L4

Rollback

Turning a deployment off after it went wrong. L6

Rolling blackout

The grid shedding load on purpose so it does not collapse by accident. L1

Router

The layer picking which model gets your request. Invisible, and it sets your bill. L5

Safe harbour

A rule that protects you if you follow it exactly. Narrow, and everyone tests the edges. Band

Sandbox

A walled space where an agent can act without breaking anything real. L5

Scaling law

The observed rule linking compute, data and capability. Everything is bet on it. L4

SLA

A promise about uptime or latency with money attached to breaking it. L6

Spot price

What it costs to buy today rather than on contract. Where a shortage shows up first. L2

SPV

A separate company holding one data centre and its debt, off the parent balance sheet. Band

Study window

The period the grid operator spends deciding whether your site breaks anything. L1

Substation pad

The concrete a substation sits on. Poured long before the power arrives. L1

Survey

Somebody physically checks what is under the field before anyone spends real money. L1

Take-or-pay

You pay for the capacity whether you use it or not. What makes lenders comfortable. Band

Tape-out

Sending a finished design to the factory. After this, a mistake costs a year. L2

Tenancy

Whether the hardware is yours alone or shared. It changes the price and the risk. L3

Title search

Proof nobody else owns it. Slow, boring, and it kills deals. L1

token

A chunk of text a model reads or writes. Roughly three quarters of a word. L4

tokens

Chunks of text a model reads or writes. One token is roughly three quarters of a word. L4

Tool call

The model asking software to do something. Where an agent stops being a chat. L6

Tool schema

The description that tells a model how to call a piece of software. L5

Transformer lead time

The wait for the box that steps grid voltage down. Now measured in years. L1

Vendor financing

A supplier funding the customer who buys from it. Revenue that started as its own cash. Band

wafer

A disc of silicon that chips are cut from. Factories count their output in wafers per month. L2

Water permit

Permission to draw and discharge cooling water. The fight nobody sees coming. L1

Water positive

A pledge to return more water than you take. Often measured across a whole portfolio rather than site by site. L1

Yield

The share of chips on a wafer that actually work. A few points of yield is a fortune. L2

Zoning appeal

A neighbour challenging the permit. Free to file, expensive to lose. L1