> ## Documentation Index
> Fetch the complete documentation index at: https://wiki.platelunchcollective.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Keyword Search

> Keyword search is retrieval that matches the literal terms of a query against the terms in documents, ranking by lexical overlap rather than meaning.

*Core concept* · *AI Search Infrastructure*

## 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

<CardGroup cols={2}>
  <Card title="BM25" href="/ai-search-glossary/bm25">See also</Card>
  <Card title="TF-IDF" href="/ai-search-glossary/tf-idf">See also</Card>
  <Card title="Sparse retrieval" href="/ai-search-glossary/sparse-retrieval">See also</Card>
  <Card title="Semantic search" href="/ai-search-glossary/semantic-search">See also</Card>
  <Card title="Hybrid retrieval" href="/ai-search-glossary/hybrid-retrieval">See also</Card>
</CardGroup>

## Relevant Plate Lunch Collective Services

[AI SEO](https://www.platelunchcollective.com/services/ai-seo)  [Citation-Ready Content](https://www.platelunchcollective.com/services/citation-ready-content)