Decoder. plain-English AI glossary

Generalization

● Core

The whole point — doing well on data the model has never seen, not just the examples it trained on.

Think of it like

Learning to ride any bike, not just the exact one you practiced on.

Example

A well-generalized spam filter catches brand-new scam wording it never saw in training.

How it actually works

Generalization is the gap between training performance and real-world performance. Everything in ML — regularization, validation sets, more data — is ultimately in service of closing it. Overfitting and underfitting are the two ways it breaks.

For product teams

It’s the only performance number that matters — measure on data the model hasn’t seen.

For engineers

Expected performance on the true data distribution, estimated via held-out/test error.

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