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Keyword search guides
7 published guides. Start with What is keyword search.
How lexical search matches exact terms, why it is still hard to beat on precise queries, and where it breaks.
Read the guideLearning path
All guides
Understand it1 guides
How it works6 guides
ExplainerBM25 algorithmThe BM25 formula term by term, what k1 and b tune, and why it remains a strong baseline.ExplainerTF-IDFHow term frequency and inverse document frequency score relevance, with a worked example.ExplainerInverted indexThe data structure behind keyword search, how it is built and why it makes exact matching fast.ExplainerFull-text searchFull-text search features like stemming, phrase and fuzzy matching, and the vocabulary gap they cannot close.ExplainerVocabulary mismatch problemWhy users and documents describe the same thing with different words, and every fix from synonyms to embeddings.ExplainerStemming, lemmatization and analyzersHow analyzers normalise text before indexing and how those choices change keyword matching.