What Is DefinedTerm Schema?

How DefinedTerm Schema Works

DefinedTerm is a type in the Schema.org vocabulary that describes, in its own words, “a word, name, acronym, phrase, etc. with a formal definition.” It exists so that a glossary entry, a taxonomy label, or a subject-classification term can be expressed as structured data rather than as plain prose that a machine has to infer meaning from. It was added to Schema.org’s core vocabulary in 2018 and sits in the type hierarchy under Intangible, which itself descends from the root Thing.

In practice you express a DefinedTerm as JSON-LD in the page’s markup. The @type is set to DefinedTerm, the name property holds the term being defined, and the description property holds the definition itself. If the term has an alphanumeric code — the way a medical or industry classification might — that goes in termCode. Crucially, the inDefinedTermSet property links the entry to a DefinedTermSet: the container that represents the whole glossary or vocabulary the term belongs to.

Unlike FAQPage markup in its heyday, DefinedTerm has never had a dedicated Google rich result. Adding it will not change how the page looks in search results. What it does is make the page’s meaning explicit to systems that consume structured data — search engine knowledge graphs and, increasingly, the retrieval layers behind AI answers — by asserting that a given string is a defined term, that a given block of text is its definition, and that both belong to a named set.

Components of a DefinedTerm

The Schema.org specification recommends a small, focused set of properties:

• name — the term being defined (for example, “Hreflang”).
• description — the formal definition of that term.
• termCode — an alphanumeric code for the term within its set, used when a controlled vocabulary assigns codes (optional).
• inDefinedTermSet — a reference, by URL or nested object, to the DefinedTermSet that contains the term.
• about — the subject the term concerns, when you want to tie it to another entity.
• url — the canonical location of the term’s own page.

A DefinedTermSet wraps the collection. It carries its own name, url, and description, and a glossary typically markup-links every individual DefinedTerm back to one shared set, so the entries read as a coherent vocabulary rather than a scatter of unrelated definitions.

Example of DefinedTerm Schema

The clearest documented model is Schema.org’s own type reference, which defines DefinedTerm and prescribes exactly how to use it. Per the official specification, a single glossary entry is marked up by setting @type to DefinedTerm, placing the headword in name, the definition in description, and pointing inDefinedTermSet at the glossary’s DefinedTermSet. A term with a formal code — say an entry in a classification system — additionally carries that code in termCode.

Concretely, a glossary entry for the term “Canonicalization” would be a DefinedTerm whose name is “Canonicalization,” whose description is the one- or two-sentence definition, and whose inDefinedTermSet references a DefinedTermSet named “SEO Glossary” living at the glossary’s index URL. Repeat that structure for every entry, all pointing at the same set, and the whole glossary becomes a typed, connected vocabulary.

The scale of real-world use is documented too: Schema.org’s own type page reports that DefinedTerm appears on somewhere between 10,000 and 100,000 domains in Google’s sample of the web — meaningful adoption for a type with no rich-result payoff, which tells you the sites using it are doing so for semantic structure rather than a SERP prize. The mechanism is exactly what it looks like: no special search feature, just a clean, standard way to publish definitions as machine-readable entities and bind them into a named set.

Frequently Asked Questions

The Bottom Line

DefinedTerm is the vocabulary Schema.org gives you for saying, in a way machines can parse, "here is a term and here is what it means." It won no rich result and never will, but it turns a page of human prose into typed, connectable knowledge — each entry a defined entity, all of them bound to a named set. Adopt it for legibility to search engines and AI, not for a SERP makeover.