{
  "altLabels": [
    "Okapi BM25"
  ],
  "definition": "A term-based ranking function that scores documents for a query using term frequency, inverse document frequency, and document-length normalization.",
  "derivedRelations": [
    {
      "note": "BM25 scores documents using term statistics; exact match requires specified terms, values, or phrases to match exactly.",
      "target": "exact-match",
      "type": "notEquivalentTo"
    },
    {
      "target": "exact-match",
      "type": "related"
    }
  ],
  "distinctions": [
    {
      "reason": "BM25 is the standard BM25 scoring function; BM25F is a field-aware variant for structured or fielded documents.",
      "statement": "BM25 is not BM25F.",
      "target": "bm25f",
      "targetLabel": "BM25F",
      "targetUri": "https://id.searchplex.net/bm25f/"
    },
    {
      "reason": "BM25 is a ranking function; an inverted index is an index structure commonly used to retrieve postings for lexical scoring.",
      "statement": "BM25 is not Inverted Index.",
      "target": "inverted-index",
      "targetLabel": "Inverted Index",
      "targetUri": "https://id.searchplex.net/inverted-index/"
    },
    {
      "reason": "BM25 is a scoring method; keyword search is a practitioner-facing search style that may use BM25 or other lexical methods.",
      "statement": "BM25 is not Keyword Search.",
      "target": "keyword-search",
      "targetLabel": "Keyword Search",
      "targetUri": "https://id.searchplex.net/keyword-search/"
    },
    {
      "reason": "BM25 is one lexical scoring method; lexical retrieval is the broader retrieval family based on lexical features.",
      "statement": "BM25 is not Lexical Retrieval.",
      "target": "lexical-retrieval",
      "targetLabel": "Lexical Retrieval",
      "targetUri": "https://id.searchplex.net/lexical-retrieval/"
    },
    {
      "reason": "BM25 uses sparse lexical evidence, but sparse retrieval also includes other traditional and learned sparse approaches.",
      "statement": "BM25 is not Sparse Retrieval.",
      "target": "sparse-retrieval",
      "targetLabel": "Sparse Retrieval",
      "targetUri": "https://id.searchplex.net/sparse-retrieval/"
    },
    {
      "reason": "BM25 and TF-IDF are both classical lexical weighting approaches, but BM25 adds probabilistic term saturation and document-length normalization.",
      "statement": "BM25 is not TF-IDF.",
      "target": "tf-idf",
      "targetLabel": "TF-IDF",
      "targetUri": "https://id.searchplex.net/tf-idf/"
    }
  ],
  "id": "bm25",
  "kind": "Method",
  "license": "https://creativecommons.org/publicdomain/zero/1.0/",
  "links": [
    {
      "label": "The Probabilistic Relevance Framework: BM25 and Beyond",
      "type": "canonicalSurvey",
      "url": "https://www.staff.city.ac.uk/~sbrp622/papers/foundations_bm25_review.pdf"
    }
  ],
  "modifiedAt": "2026-09-14T06:43:46Z",
  "prefLabel": "BM25",
  "publisher": {
    "name": "Searchplex",
    "url": "https://searchplex.net/"
  },
  "relations": [
    {
      "note": "BM25 is the standard BM25 scoring function; BM25F is a field-aware variant for structured or fielded documents.",
      "target": "bm25f",
      "type": "notEquivalentTo"
    },
    {
      "note": "BM25 is a ranking function; an inverted index is an index structure commonly used to retrieve postings for lexical scoring.",
      "target": "inverted-index",
      "type": "notEquivalentTo"
    },
    {
      "note": "BM25 is a scoring method; keyword search is a practitioner-facing search style that may use BM25 or other lexical methods.",
      "target": "keyword-search",
      "type": "notEquivalentTo"
    },
    {
      "note": "BM25 is one lexical scoring method; lexical retrieval is the broader retrieval family based on lexical features.",
      "target": "lexical-retrieval",
      "type": "notEquivalentTo"
    },
    {
      "note": "BM25 uses sparse lexical evidence, but sparse retrieval also includes other traditional and learned sparse approaches.",
      "target": "sparse-retrieval",
      "type": "notEquivalentTo"
    },
    {
      "note": "BM25 and TF-IDF are both classical lexical weighting approaches, but BM25 adds probabilistic term saturation and document-length normalization.",
      "target": "tf-idf",
      "type": "notEquivalentTo"
    },
    {
      "target": "bm25f",
      "type": "related"
    },
    {
      "target": "hybrid-retrieval",
      "type": "related"
    },
    {
      "target": "inverted-index",
      "type": "related"
    },
    {
      "target": "keyword-search",
      "type": "related"
    },
    {
      "target": "lexical-retrieval",
      "type": "related"
    },
    {
      "target": "sparse-retrieval",
      "type": "related"
    },
    {
      "target": "tf-idf",
      "type": "related"
    },
    {
      "target": "ranking",
      "type": "usedFor"
    },
    {
      "target": "retrieval",
      "type": "usedFor"
    }
  ],
  "representations": {
    "html": "https://id.searchplex.net/bm25/",
    "json": "https://id.searchplex.net/bm25.json",
    "jsonld": "https://id.searchplex.net/bm25.jsonld"
  },
  "scheme": "https://id.searchplex.net/scheme/",
  "scopeNote": "BM25 is a widely used lexical retrieval and ranking method. It is often used as a baseline or component in keyword, lexical, sparse, and hybrid retrieval systems, but it is not itself the same as keyword search, lexical retrieval, or sparse retrieval.",
  "status": "published",
  "uri": "https://id.searchplex.net/bm25/"
}