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Hallucination
NLP/dictionary/hallucination
Definition
When an LLM produces output that looks like an answer but isnt grounded in anything real. Not a bug — the consequence of next-token prediction applied to questions where the right answer wasnt available.
Posts that use this term
- RAG: giving a model memory it doesn't have
RAG is the pattern of fetching relevant text from a search system and putting it in the LLM's context window before asking your question. Not magic, not fine-tuning — just better prompts.
- The context window, and why models hallucinate
An LLM only sees a fixed-size slice of text at a time. When it doesn't know something, it predicts anyway — that's a hallucination, not a bug.