> ## 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.

# Cluster (Vector Space)

> A cluster is a region in vector space where semantically similar texts are grouped.

*Technical implementation* · *AI Search Infrastructure*

## Definition

A cluster is a region in vector space where semantically similar texts are grouped. Content about the same topic occupies nearby positions; content about different topics occupies distant positions. Retrieval finds the content nearest to a query's position in this space.

## Why It Matters for AI Search

Understanding clusters explains why mixed-topic content retrieves poorly for everything. A passage that splits its meaning between two topics lands between two clusters — close to neither one. A passage that stays within one cluster retrieves consistently for all queries that land in that region. The structural instruction — one topic per section — is a geometric instruction: stay inside one cluster.

## Related Terms

<CardGroup cols={2}>
  <Card title="Semantic center of gravity" href="/ai-search-glossary/semantic-center-of-gravity" />

  <Card title="Embedding drift" href="/ai-search-glossary/embedding-drift" />

  <Card title="Topic coherence" href="/ai-search-glossary/topic-coherence" />

  <Card title="Cosine similarity" href="/ai-search-glossary/cosine-similarity" />

  <Card title="Vector database" href="/ai-search-glossary/vector-database" />
</CardGroup>

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