AI engineering glossary · RAG vector search
What is hallucination?
Hallucination: When a language model states something fluent but unsupported or false, such as an invented figure or citation. RAG reduces it by supplying evidence, but the model can still add claims that the retrieved text does not contain.
Hallucination: an example
The bot says the refund window is 45 days, but the retrieved policy says 30.
Related terms
More RAG vector search terms
- Hamming distance
- Hierarchical chunking
- HNSW
- Hybrid search
- HyDE
- Index refresh
- Ingestion pipeline
- Inverted index
Where you learn it
Hallucination is part of the AI Engineering Program, which teaches it with notes, a hands-on lab and an exam. The first lesson is free.