Hallucination
An AI-generated statement, citation, image detail, or answer that sounds plausible but is false, unsupported, or invented.
“The chatbot hallucinated a court case that did not exist.”
Use the term for confident model errors, not for ordinary uncertainty or a person having a medical hallucination.
AI researchers adopted the word by analogy to perception without a real external basis, though some experts criticize the metaphor.
AI hallucination
The full phrase for a fabricated model output.
model fabrication
A more literal alternative.
Why do AI models hallucinate?
They generate likely patterns rather than directly verifying every claim against reality.
Can hallucinations be eliminated?
They can be reduced with retrieval, constraints, and verification, but not universally eliminated.