Hallucination
Also called hallucinate, hallucinated, confabulation
When an AI states something false or made up as if it were fact, often fluently and with confidence.
A hallucination is an AI answer that sounds right and isn't: an invented statistic, a quote nobody said, a court case that never happened, a real author with a fake book. It isn't a glitch on a bad day. It comes from how models work: they produce the most plausible continuation, and their training rewards a confident guess over "I don't know".
Hallucinations cluster where facts are specific and rare: exact titles, dates, figures, links, and anything about small organisations or private people. Common knowledge is usually fine. So the useful question isn't "does this AI hallucinate?" (they all can) but "which part of this answer would hurt if it were invented?"
For example
A consultancy's report to the Australian government cited research that didn't exist and a judge's quote nobody said; the firm later disclosed it had used AI and refunded part of its fee.
Put it to use
Where you'll meet hallucination in ChatGPT, Gemini and Claude, how to use it there, and the mix-up most people make.
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