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DefinedTerm Schema: Why Glossaries Need It for AEO

DefinedTerm schema is structured markup that labels a term and its definition for AI search engines. Without it, your glossary is plain text — with it, it becomes a citable answer source.

Par Daniel MercerPublié le 30 mai 20265 min de lecture

DefinedTerm schema is a Schema.org type that explicitly marks up a word or phrase alongside its definition, enabling AI search engines and answer engines to extract, cite, and surface your glossary content with precision. If you run a glossary and skip this markup, you are leaving AEO real estate on the table.

What Is DefinedTerm Schema?#

DefinedTerm (schema.org/DefinedTerm) is a structured data type used to identify a concept that has a formal, bounded definition within a specific context — usually a DefinedTermSet such as a glossary, taxonomy, or controlled vocabulary. It pairs a name (the term) with a description (the definition) and optionally links to the broader set it belongs to.

This is distinct from plain FAQ schema or Article schema. Those tell search engines that content exists. DefinedTerm tells them what a word means — a signal AI answer engines weight heavily when generating definitional responses.

How Does DefinedTerm Schema Work?#

At its core, the markup wraps each glossary entry with three key properties:

@type: DefinedTerm
name: the term being defined (e.g., "Canonical Tag")
description: the concise, authoritative definition
inDefinedTermSet: a reference to the parent glossary (DefinedTermSet), which adds relational context
url: the canonical URL of the term's own page or anchor

Search crawlers and LLM-based answer engines parse this markup to confirm that your page is not just mentioning a term but authoritatively defining it. That distinction drives citation selection in tools like Google's AI Overviews and Bing Copilot.

JSON-LD Implementation Example

json

{
  "@context": "https://schema.org",
  "@type": "DefinedTerm",
  "name": "Canonical Tag",
  "description": "An HTML link element that tells search engines which URL is the preferred version of a page, preventing duplicate content issues.",
  "url": "https://example.com/glossary#canonical-tag",
  "inDefinedTermSet": {
    "@type": "DefinedTermSet",
    "name": "SEO Glossary",
    "url": "https://example.com/glossary"
  }
}

Place this JSON-LD block in the <head> or inline <script> of each glossary entry page. If your glossary lives on a single paginated page, emit one block per term.

Why Does DefinedTerm Schema Matter for AEO?#

Answer Engine Optimization (AEO) is the practice of structuring content so AI-powered answer surfaces select it as a citation. AI search engines favor content that is:

Unambiguous — the term and definition are explicitly paired, not inferred
Contextually bounded — the definition lives within a known, labeled set
Canonically attributed — a url signals the authoritative source

Plain prose definitions satisfy none of these criteria structurally. DefinedTerm schema satisfies all three. When an AI engine encounters a user query like "what is a canonical tag," it prefers sources that have formally declared this is a definition over sources that merely include the word in a paragraph.

How Is DefinedTerm Different from FAQ Schema?#

FAQ schema (FAQPage) marks up question-and-answer pairs. The question can be anything — a how-to, an opinion, a comparison. DefinedTerm is semantically narrower: it signals a word has a meaning, not a question has an answer. For glossaries, DefinedTerm is the correct type. Using FAQ schema for definitions is a semantic mismatch that dilutes the signal.

What Is a DefinedTermSet?#

A DefinedTermSet is the parent container for a collection of DefinedTerms — your entire glossary. Declaring it gives AI engines relational context: these terms belong together, they share an authoring domain, and the set itself is a named resource. This relational layer strengthens topical authority signals across your entire vocabulary.

Add a single DefinedTermSet block on your glossary index page:

json

{
  "@context": "https://schema.org",
  "@type": "DefinedTermSet",
  "name": "SEO & AEO Glossary",
  "description": "Definitions of core terms in search engine optimization and answer engine optimization.",
  "url": "https://example.com/glossary"
}

How Do You Implement DefinedTerm Schema Efficiently?#

For small glossaries, hand-coding JSON-LD is practical. For glossaries with dozens or hundreds of terms, use a schema generation tool. The SeoChatAI Schema Generator outputs DefinedTerm and DefinedTermSet markup without requiring you to write JSON by hand — reducing syntax errors that silently invalidate your structured data.

Steps for a clean implementation:

Audit your glossary: list every term and its current URL or anchor
Write one precise definition per term (25–90 words works best for answer engine excerpts)
Generate the JSON-LD for each term using a reliable tool
Add the DefinedTermSet block to your glossary index
Validate each block via Google's Rich Results Test or Schema Markup Validator
Monitor impressions and AI Overview appearances in Search Console

What Properties Should Every DefinedTerm Include?#

At minimum, include @type, name, description, and url. Additionally:

inDefinedTermSet: strongly recommended — ties the term to its authoritative collection
sameAs: optional URL to a Wikidata or Wikipedia entry for the concept, boosting entity disambiguation
termCode: used in formal taxonomies (e.g., medical or legal) — skip for general SEO glossaries

Omitting description is the most common mistake. Without it, the markup declares a term exists but does not supply the answer — defeating the entire AEO purpose.

Common Mistakes to Avoid#

Nesting DefinedTerm inside Article schema without also emitting a standalone block — the relational signal gets lost
Using @type: Thing instead of DefinedTerm for glossary entries — too generic to trigger definitional features
Writing definitions over 200 words — answer engines excerpt short spans; long definitions dilute the extractable answer
Skipping url — without a canonical URL, the citation has no destination to surface

For teams managing large content operations, running your glossary pages through the SeoChatAI Schema Generator catches these issues before they reach production.

Key Takeaway#

DefinedTerm schema is not optional decoration for glossary pages — it is the structured signal that transforms a page of text into a machine-readable definition source. AI answer engines are trained to prefer explicit, bounded, attributed definitions. Implement DefinedTerm correctly and your glossary becomes infrastructure for AEO, not just reference content for human readers.

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Publié le 30 mai 2026

Questions fréquentes

What is DefinedTerm schema?

DefinedTerm schema is a Schema.org structured data type that labels a specific term and its formal definition on a web page. It tells search engines and AI answer engines that a page is authoritatively defining a concept, not merely mentioning it — making it a core tool for glossaries and AEO.

How is DefinedTerm schema different from FAQ schema?

FAQ schema marks up any question-and-answer pair. DefinedTerm is semantically specific: it declares that a named term has a bounded definition. For glossary pages, DefinedTerm is the correct and more precise type. Using FAQ schema for definitions sends a weaker, mismatched signal to AI search engines.

Do I need a DefinedTermSet for my glossary?

Yes. A DefinedTermSet groups all your DefinedTerm entries under a named, authoritative collection. This relational context helps AI engines understand that your glossary is a coherent, topically bounded resource — strengthening topical authority and improving the chance each term gets cited in answer results.

How long should a DefinedTerm description be?

Aim for 25–90 words per definition. Answer engines extract short, precise spans when generating responses. Definitions under 25 words may lack sufficient context; definitions over 150 words risk diluting the extractable answer and reduce the likelihood of a clean AI citation.

Does DefinedTerm schema create rich results in Google?

DefinedTerm does not currently trigger a dedicated SERP rich result the way Recipe or FAQ schema does. Its value is in AEO: it improves selection probability for AI Overviews, Bing Copilot, and similar answer surfaces by providing unambiguous, machine-readable definitional signals.

What is the most common DefinedTerm schema mistake?

Omitting the `description` property. Without it, the markup declares a term exists but provides no definition — defeating the entire purpose. Other frequent errors include skipping `url`, using the generic `Thing` type instead of `DefinedTerm`, and failing to link terms to a parent `DefinedTermSet`.

Can I use DefinedTerm schema on a single-page glossary?

Yes. Emit one JSON-LD DefinedTerm block per term, using anchor URLs (e.g., `/glossary#canonical-tag`) as the `url` property for each entry. Also include a single DefinedTermSet block for the page itself. Validators like Google's Rich Results Test will confirm each block is parsed correctly.