Hallucination
1 min read · Reviewed 17 Oct 2026
In short
When an AI states something false as if it were true.
In plain English
An AI does not know facts the way a reference book does. It predicts what text should come next. Usually that lands on the truth, because the truth is what it mostly saw during training. Sometimes it doesn't — and the wrong answer arrives in exactly the same confident tone as a right one.
A real example
Ask for sources on a niche topic and you may get three perfectly formatted references — plausible authors, plausible journals, plausible years — that do not exist. Nothing in the phrasing signals the difference.
Why it matters
Confidence is not accuracy. Anything you would be embarrassed to get wrong — a name, a number, a legal point, a citation — gets verified outside the AI before you use it.
