DefinedTerm is a Schema.org type for a word, name, acronym or phrase that has a formal definition, and DefinedTermSet is a collection of them, such as a glossary. A term has a name, a description holding the definition, and inDefinedTermSet pointing to its set. Google does not offer a rich result for DefinedTerm, so its value is in describing glossary content precisely.
Markup outline
On a glossary entry page, the DefinedTerm can be the mainEntity of the page, with a termCode for an acronym if useful. The glossary index can carry a DefinedTermSet listing its terms with hasDefinedTerm.
{
"@context": "https://schema.org",
"@type": "DefinedTerm",
"name": "Net revenue retention",
"termCode": "NRR",
"description": "Recurring revenue kept from existing customers over a period, including expansion and churn.",
"inDefinedTermSet": {
"@type": "DefinedTermSet",
"name": "Hollowmere SaaS metrics glossary",
"url": "https://www.hollowmere.example/glossary"
}
}What it can and cannot do
Validators accept it, and any parser that reads Schema.org can use it. The Rich Results Test will not report it, because Google has no feature for it. Some SEOs add it to glossaries hoping it helps AI systems recognize definitions; that is plausible as clear description, but no vendor has documented using it.
Example
A SaaS metrics glossary
Hollowmere, a subscription analytics vendor, runs a glossary of SaaS metrics. Each entry page carries DefinedTerm markup inside a WebPage and an Article for the long explanation, with the term linked to the glossary's DefinedTermSet. The team validates it with the Schema Markup Validator, since the Rich Results Test shows nothing for this type.
Common mistakes
Expecting a definition rich result
Google has no DefinedTerm feature. Definition boxes in search come from Google's own systems.
Questions
Both can be accurate: DefinedTerm for the concept and its definition, Article for a long explanatory page. Use them together if it fits.
