AI engineering glossary · RAG vector search
What is inverted index?
Inverted index: A data structure that maps each term to the list of documents containing it, like the index at the back of a book. It makes keyword lookups fast and is the basis of search engines and BM25 scoring.
Inverted index: an example
The term 'GST' points to documents 4, 19 and 203, so a query for 'GST' reads only those three.
Related terms
More RAG vector search terms
- IVF
- Knowledge base
- Knowledge graph
- Late interaction
- Layout-aware parsing
- Learned sparse retrieval
- LLM-as-judge
- Locality-sensitive hashing
Where you learn it
Inverted index is part of the AI Engineering Program, which teaches it with notes, a hands-on lab and an exam. The first lesson is free.