# Hallucinations

> Fluent, confident output that is false or unsupported — invented facts, figures, quotes or sources — presented as if it were true.

Source: Promptea — https://www.promptea.me/en/glossary/hallucinations · Language: English · Last updated: 2026-11-09

## What it means

- Definition: a language model generates plausible text, not verified facts. When it lacks the information, it can still produce a convincing answer that happens to be wrong.
- Why it matters: the output reads well, so errors are easy to miss. The risk is highest for specific details — numbers, dates, quotations, citations, API names.
- How to reduce it: give the grounding material in the prompt and say to answer only from it; allow 'I don't know' or 'not enough information'; ask it to mark what it is unsure of; for current facts use a tool that searches and returns sources.
- Common mistake: trusting a source the model produced without opening it. Prompting lowers the rate of invented content but does not eliminate it — verify anything that matters.

## Example

```text
Answer using only the context below.
If the answer is not in the context, reply exactly: "Not enough information".
For every claim, quote the sentence from the context that supports it.

Context:
"""[paste]"""

Question: [question]
```

[Open in Promptea](https://www.promptea.me/en/analyzer?prompt=Answer+using+only+the+context+below.%0AIf+the+answer+is+not+in+the+context%2C+reply+exactly%3A+%22Not+enough+information%22.%0AFor+every+claim%2C+quote+the+sentence+from+the+context+that+supports+it.%0A%0AContext%3A%0A%22%22%22%5Bpaste%5D%22%22%22%0A%0AQuestion%3A+%5Bquestion%5D&purpose=text&target=gemini)

## Frequently asked questions

### Can a prompt eliminate hallucinations?

No. Grounding the answer in supplied text, allowing 'I don't know' and requiring supporting quotes lower the rate a lot, but you still need to check facts that matter.

### Are some tasks more prone to it?

Yes: questions about obscure or recent facts, requests for citations, exact figures and long chains of reasoning. Tasks that transform text you supply (summarize, extract, rewrite) are safer.

## Related

- [Prompts for Perplexity: grounded answers from the web](https://www.promptea.me/en/guides/perplexity-prompt-guide)
- [Context engineering: how to structure what you give an AI for better outputs](https://www.promptea.me/en/guides/context-engineering)
- [How to debug a prompt that gives bad output](https://www.promptea.me/en/guides/prompt-debugging)
- [Retrieval-augmented generation (RAG)](https://www.promptea.me/en/glossary/retrieval-augmented-generation)
- [Evaluation](https://www.promptea.me/en/glossary/evaluation)