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AI Glossary

45 AI words in plain language, each linked to the lesson where you can try it for yourself.

A4
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The share of predictions a model gets right. It can hide poor results for small groups.
Try it in Where AI goes wrong
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The curve a neuron passes its total through, such as sigmoid or ReLU. It lets networks learn non-straight patterns.
Try it in Weights and bias
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Software that does tasks we link with human thinking, today mostly by learning patterns from data.
Try it in AI or not? The sorting game
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A clear list of steps for solving a problem.
Try it in Rules vs learning
B3
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The method that sends error backwards through a network to work out how to adjust each weight.
Try it in Layers: going deep
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When data or a model treats some groups unfairly, often because they were under-represented.
Try it in Where AI goes wrong
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A number added to a neuron's total that makes it more or less eager to fire.
Try it in One neuron, three knobs
C4
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A program you talk to in text or speech. Modern ones use large language models.
Try it in AI in your day
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Predicting a category, such as spam or safe.
Try it in Build a spam detector
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Finding natural groups in data without any labels.
Try it in K-means clustering
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Testing on several different splits of the data and averaging, for a steadier score.
Try it in Training vs testing, and overfitting
D3
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The examples a model learns from.
Try it in Data, model, feedback
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An organised collection of examples.
Try it in Data, model, feedback
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Machine learning with neural networks that have many layers.
Try it in Layers: going deep
E1
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One full pass through the training data.
Try it in Build a digit guesser
F2
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A number that describes an example, such as weight or length.
Try it in Features: how machines see data
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A signal telling a model how right or wrong it was.
Try it in Data, model, feedback
G1
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Learning by repeatedly stepping downhill on the error.
Try it in How networks learn
H2
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When an AI confidently states something false or made up.
Try it in Where AI goes wrong
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Neurons between a network's input and output, combining simple patterns into complex ones.
Try it in Layers: going deep
K1
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A clustering method that alternates assigning points and moving group centres.
Try it in K-means clustering
L4
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The right answer attached to a training example.
Try it in Build a spam detector
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How big each training step is. Too big blows up, and too small is slow.
Try it in How networks learn
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A small valley in the error that isn't the lowest point overall.
Try it in How networks learn
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A number measuring how wrong a model is. Training tries to lower it.
Try it in How networks learn
M2
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Teaching computers from examples instead of writing every rule.
Try it in Build a spam detector
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What's left after training: the thing that makes predictions.
Try it in Data, model, feedback
N4
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A simple classifier that combines how often each word appears in each class.
Try it in Build a spam detector
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AI built for one specific task. All of today's everyday AI tools are narrow.
Try it in AI in your day
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A model made of connected simple units (neurons) arranged in layers.
Try it in One neuron, three knobs
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A small unit that multiplies inputs by weights, adds them up and decides.
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O2
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An example very different from the rest, which can drag a model off course.
Try it in Linear regression
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Memorising the training data so well that new data is handled badly.
Try it in Training vs testing, and overfitting
P3
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An early single-neuron learning model, built by Frank Rosenblatt in 1958.
Try it in One neuron, three knobs
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One tiny dot of an image. To a computer, it's just a number.
Try it in Build a digit guesser
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A model's output for a new example.
Try it in AI in your day
R1
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Predicting a number, such as rent or marks.
Try it in Linear regression
S2
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An S-shaped curve that squashes any number to between 0 and 1.
Try it in Weights and bias
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Learning from examples that come with the right answers.
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T2
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Examples hidden during training and used for an honest score.
Try it in Training vs testing, and overfitting
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Adjusting a model's numbers to make fewer mistakes on examples.
Try it in Weights and bias
U2
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A model too simple to capture the pattern, even on training data.
Try it in Training vs testing, and overfitting
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Finding structure in data without any right answers given.
Try it in K-means clustering
W1
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A number that sets how much an input counts, and in which direction.
Try it in Weights and bias
X1
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“Exactly one is on”. A pattern a single neuron can't learn but a hidden layer can.
Try it in Layers: going deep