Definition
DefinedTerm is a Schema.org type for 'a word, name, acronym, phrase, etc. with a formal definition', in the words of the Schema.org specification. It is used for glossary entries, dictionaries, taxonomies and controlled vocabularies. A companion type, DefinedTermSet, describes the collection a term belongs to, such as a glossary or an industry classification scheme.
The markup is small. The name property holds the term itself and description holds its definition. termCode is optional and holds a code when the term has one, such as an ICD diagnosis code or an internal category ID. inDefinedTermSet points to the parent DefinedTermSet by object or URL, and the set lists its terms with hasDefinedTerm. Because DefinedTerm inherits from Thing, it also accepts alternateName for synonyms and abbreviations, sameAs for equivalent entries elsewhere (for example a Wikidata item), and url for the term's own page.
Google does not offer a rich result for DefinedTerm, and its May 2026 guide to generative AI features says no special Schema.org markup is needed to appear in AI Overviews or AI Mode. So the value is not a Google display feature. It is clarity for any system that parses structured data: other search engines, site search, internal knowledge bases, data aggregators and agent protocols such as NLWeb that return Schema.org objects. It tells those systems which string is the term, which text is the definition and which vocabulary it belongs to.
Two cautions follow from how AI assistants read pages. First, a 2025 searchVIU test found that ChatGPT, Claude, Perplexity, Gemini and AI Mode did not read JSON-LD when fetching pages live, so the definition must also be visible on the page, ideally as the first sentence. Second, the markup has to match the visible text exactly; a definition that exists only in markup, or differs from the copy, is the kind of mismatch Google's structured data guidelines warn against.
In practice, glossaries work best with one URL per term. A focused page whose first paragraph states the definition gives retrieval systems a clean passage to cite, which suits sub-document retrieval and makes each term its own entity with its own internal links. Pair the DefinedTerm with a DefinedTermSet on the glossary index page, link related terms to each other, and keep the visible definition short enough to quote. FAQPage markup can still sit on the same page as valid Schema.org data, although Google stopped showing FAQ rich results in May 2026.
DefinedTerm will not make a weak definition authoritative. The definition itself, its accuracy and its originality, decides whether an assistant cites it; the markup only removes ambiguity about what the definition is. See structured content and answer-ready content for the writing side.
Examples of DefinedTerm Schema
- A payments company's glossary gives each of its 140 terms a page with DefinedTerm markup whose description matches the first visible sentence, and the glossary index page carries a DefinedTermSet listing every term.
- A medical publisher marks up condition pages with DefinedTerm and a termCode holding the ICD-10 code, so downstream tools can match its definitions to clinical data.
- A software vendor coins a term for its product category and uses DefinedTerm with alternateName for the two spellings customers use, plus a visible definition on a dedicated page.
- An industry association publishes its official skills taxonomy as a DefinedTermSet so training providers and job boards can reference the same definitions.
