> ## 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.

# Ontology

> An ontology is a formal representation of knowledge within a domain — defining the entities, concepts, properties, and relationships that exist within that d...

*Technical implementation* · *Entity & Knowledge Graph*

## Definition

An ontology is a formal representation of knowledge within a domain — defining the entities, concepts, properties, and relationships that exist within that domain and how they relate to each other. Schema.org is a practical ontology for web content; Wikidata uses an ontology to structure its knowledge base.

## Why It Matters for AI Search

Ontologies are the conceptual architecture that knowledge graphs are built on. When a brand implements schema.org markup, it is placing itself within a shared ontology that AI systems use to understand what the brand is and how it relates to other entities. Understanding ontology helps explain why using the correct schema.org type — and the correct properties for that type — matters more than creative improvisation with custom markup.

## Related Terms

<CardGroup cols={2}>
  <Card title="Schema.org" href="/ai-search-glossary/schemaorg" />

  <Card title="Entity type" href="/ai-search-glossary/entity-type" />

  <Card title="Knowledge graph" href="/ai-search-glossary/knowledge-graph" />

  <Card title="Entity schema" href="/ai-search-glossary/entity-schema" />

  <Card title="Wikidata" href="/ai-search-glossary/wikidata" />
</CardGroup>

## Relevant Plate Lunch Collective Services

[Entity SEO](https://www.platelunchcollective.com/services/entity-seo)