BM25

BM25 helps rank search results by checking how well a document matches the search words.

What it does

BM25 helps rank search results by checking how well a document matches the search words.

Relevance: How well a result matches • Saturation: Stopping counting

How it works

• Count matching words.
• Adjust for very long or very short documents.
• Rank the best matches higher.

Uses and applications

• A website search box can show the best pages first.
• A help center can find the right support article.
• An online store can rank products that match your search.

In short

BM25 is used for search ranking.

Related methods

• TF-IDF: The simpler word-weighting idea BM25 builds on.
• RAG (Open Book AI): Retrieves documents with methods like BM25 before generating an answer.

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