Skip to main contentHallucination explained — Plausible output without a sound basis
An AI produces false, unsupported or source-inconsistent content in fluent language. Confident wording can still be wrong.
An everyday example
An assistant supplies a convincing book title and page number, but the book does not exist.
When you’ll encounter it
Check original sources or actual results for numbers, quotations, biographies and commands.
What to watch for
Web access, citations and reduced randomness do not eliminate hallucinations. Check that a citation exists and supports the claim.
Related terms & sources
Prepared from the public sources below. Examples illustrate the concept. Reviewed on 2026-10-15.