Decoder. plain-English AI glossary

Hidden state

● Core

The model’s running scratchpad — the numbers it carries in its head between input and answer.

Think of it like

Your train of thought mid-sentence: not the words on the page yet, just the shape of what you’re about to say.

Example

When a chatbot “remembers” the start of your paragraph while finishing it, that memory lives in the hidden state, not the visible text.

How it actually works

At each layer, every token gets a vector of numbers — its hidden state — that encodes meaning-so-far. These aren’t words; they’re high-dimensional representations the next layer reads and rewrites. The final one gets turned back into a prediction over the vocabulary.

For product teams

It’s the internal “understanding” you can’t see and can’t directly edit — only shape through inputs.

For engineers

The intermediate activation vector at a given layer and position, dimension d_model, passed forward through the stack.

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