Definition
Keyword search is retrieval that matches the literal terms of a query against the terms in documents, ranking by lexical overlap rather than meaning. It is the classical form of search, powered by methods like TF-IDF and BM25, and it still underlies the sparse half of hybrid systems.Why It Matters for AI Search
Even in an AI search world, the exact word still matters. Keyword search rewards content that contains the specific terms a buyer types, which is why proper names, part numbers, and precise phrases belong on the page in plain text. Semantic methods can find a page by meaning, but they can also smooth over the specifics that keyword search would have matched exactly. The durable move is to state the exact terms and the surrounding meaning together, so both retrieval paths stay open.Related Terms
BM25
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TF-IDF
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Sparse retrieval
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Semantic search
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Hybrid retrieval
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