# Hallucination

> Hallucination: Fluent, confident output that is false or not supported by the input.

Canonical: https://llmdojo.dev/glossary/hallucination

Also called hallucinations.

Fluent, confident output that is false or not supported by the input.

Learn it in the lesson: [Likely is not the same as true](https://llmdojo.dev/learn/model-foundations/limits/likely-not-true) (Model Foundations · Hallucination and the Limits of Next-Token Prediction).

## Interview questions about Hallucination

- [What is a hallucination, and why can a next-token predictor produce one so fluently?](https://llmdojo.dev/interview/q/what-is-a-hallucination-and-why-can-a-next-token-predictor-produce)
- [Why do long generated answers leave more room for hallucination than one-word answers?](https://llmdojo.dev/interview/q/why-do-long-generated-answers-leave-more-room-for-hallucination-than-one)
- [You're shipping a support bot that answers from your company's policy documents. What do you put in place to reduce hallucination, and how do you evaluate it?](https://llmdojo.dev/interview/q/you-re-shipping-a-support-bot-that-answers-from-your-company-s)
- [How would you measure an LLM's answer quality and detect hallucinations against the context it was given? Then implement the evaluation component.](https://llmdojo.dev/interview/q/how-would-you-measure-an-llm-s-answer-quality-and-detect-hallucinations)
- [Design a voice assistant whose answers stay grounded. How would you reduce hallucinations?](https://llmdojo.dev/interview/q/design-a-voice-assistant-whose-answers-stay-grounded-how-would-you-reduce)
- [How would you use LLMs and vision-language models in autonomous driving, and could an LLM actually drive the car given hallucination and real-time latency limits?](https://llmdojo.dev/interview/q/how-would-you-use-llms-and-vision-language-models-in-autonomous-driving)
- [For a medical conversational AI, how would you source and split data, choose between prompting, fine-tuning and RAG, and evaluate for hallucination and unsafe advice?](https://llmdojo.dev/interview/q/for-a-medical-conversational-ai-how-would-you-source-and-split-data)
- [What is retrieval-augmented generation, and how does it reduce hallucination?](https://llmdojo.dev/interview/q/what-is-retrieval-augmented-generation-and-how-does-it-reduce-hallucination)

## Related
- [Grounding](https://llmdojo.dev/glossary/grounding)
- [Glossary of every term](https://llmdojo.dev/glossary)