Glossary
Hallucination
Confident output that is factually wrong or unsupported.
What it is
A hallucination is fluent but incorrect or fabricated output. Grounding with RAG, citations, constrained decoding, and evals are the standard mitigations in production systems.
Why it matters in production
Hallucination is the failure mode users remember. The production answer isn't hoping the model behaves — it's grounding answers in retrieved sources, making 'I don't know' an acceptable output, and measuring the rate with evals.
In practice
A bot that invents a refund policy vs one that answers only from retrieved policy chunks and says 'I don't have that information' when retrieval comes back empty.
Related terms
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