ModelRefs / Query Expansion — AI Glossary
Query Expansion — AI Glossary
Generating additional search terms or sub-queries from the original query to improve recall from the vector database.
Overview
Query expansion generates synonyms, related terms, or hypothetical answers (HyDE) to augment the original query. Multiple expansions are searched in parallel and results merged. Improves recall for under-specified queries. Pseudo-relevance feedback—expanding using top retrieved documents—is a classic IR technique adapted for dense retrieval.
Reference details
| Topic | rag |
|---|---|
| Last reviewed | 2026-06-24 |
Related terms
Commonly confused with
Adds to the query rather than replacing it: synonyms, related terms or generated variants, all searched to widen recall. That distinguishes it from rewriting, which produces one better query, and from decomposition, which produces several that each answer part of the question. HyDE is a specific expansion technique — it expands into a hypothetical answer rather than into extra terms.
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Frequently asked questions
What is Query Expansion?
Generating additional search terms or sub-queries from the original query to improve recall from the vector database.
What concepts are related to Query Expansion?
Closely related concepts include query rewriting, hyde, multi query retrieval.