What is it?
Hallucination is fluent but unsupported or incorrect generated content.
A model can produce an answer that sounds confident even when it has no reliable evidence for the claim. Fluent language is a style signal, not proof of truth.
11 · Evaluation, Safety & Reliability
What Is an AI Hallucination?
A hallucination is generated content that sounds plausible but is unsupported, fabricated, or incorrect.
Fluent language can still contain false information.
How it happens
USER QUESTION
↓MODEL GENERATES
↓CONFIDENT ANSWER
↓CHECK EVIDENCE
↓NO SUPPORTING SOURCE
↓HALLUCINATION
Fluent≠Factual
Think of it like...
Someone answers confidently from memory without checking whether the memory is correct.
Confident speaking → fluent output
Wrong memory → unsupported content
AI models do not have human intentions or beliefs.
Common forms
FABRICATED FACTInvented number, date, person, source.
UNSUPPORTED CLAIMNo evidence supports the statement.
WRONG ATTRIBUTIONCorrect-looking fact linked to wrong source.
INVENTED DETAILAdds information that was never supplied.
One simple example
POLICYRefund period: 30 days
USER“What is the refund period?”
BAD OUTPUT“60 days.”Unsupported answer
BETTER SYSTEMRetrieve policy↓Add evidence to context↓Generate answer↓Validate important field
Compare the failure
Hallucination
Incorrect or unsupported generated output.
It is an output failure, not proof of intent.
Deliberate lying
Would imply intentional deception.
AI models do not have human intentions or beliefs.
Uncertainty
The system explicitly signals it is unsure.
Hallucination may sound confident despite being wrong.
Confidence of wording is not evidence strength.
How to reduce risk
BETTER CONTEXT
RAG / RETRIEVAL
GROUNDING
VALIDATION
HUMAN REVIEW
These reduce risk. They do not guarantee perfection.
GROUNDINGConnects output to supplied evidence.
CORRECTNESSWhether the answer is actually right.
Grounded does not automatically mean correct.
Related concepts
Remember this
A hallucination is fluent but unsupported or incorrect generated content.
Video
Video
Video explainer coming soon.