BM25
Also: Okapi BM25
The standard keyword ranking function, scoring a document by how often the query's rare terms appear in it, adjusted for document length.
What people get wrong
It remains a serious baseline. On corpora full of codes, part numbers and proper nouns it routinely beats embedding search, which is why hybrid retrieval exists.
A definition is not an understanding. This is taught properly in Retrieve broadly, then rank precisely, part of Reranking & hybrid search.
Learn this properlyTerms from the same topic