# Retrieval Query Expansion and Synonyms
Status: public
Confidence: medium (0.725) (verified)
Last verified: 2026-06-02
Generation: ai_structured


## TL;DR

Query expansion and synonyms improve retrieval recall when users and documents use different words for the same concept.

## Core Explanation

Retrieval systems can miss good evidence when the query says "SLO burn" and the document says "error budget consumption." Synonyms and query expansion add controlled vocabulary bridges so search can match equivalent phrases.

Agents should treat synonym expansion as a precision-recall tradeoff. Broad synonyms can retrieve more evidence, but they can also create false matches. The safest workflow is to version synonym rules, test them against query logs, and measure retrieval quality before and after the change.

## Source-Mapped Facts

- Azure AI Search documentation describes synonym maps as resources that associate equivalent terms for search. ([source](https://learn.microsoft.com/en-us/azure/search/search-synonyms))
- Algolia documentation describes synonyms as a way to tell the engine which words and phrases should be treated as equivalent. ([source](https://www.algolia.com/doc/guides/managing-results/optimize-search-results/adding-synonyms/))
- Meilisearch documentation describes synonyms as sets of query terms that should be considered equivalent during search. ([source](https://www.meilisearch.com/docs/learn/relevancy/synonyms))

## Further Reading

- [Azure AI Search Synonyms](https://learn.microsoft.com/en-us/azure/search/search-synonyms)
- [Algolia Synonyms](https://www.algolia.com/doc/guides/managing-results/optimize-search-results/adding-synonyms/)
- [Meilisearch Synonyms](https://www.meilisearch.com/docs/learn/relevancy/synonyms)