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References and Definitions are the main mechanism within the JSON Schema standard to support re-use. Essentially a schema can be declared within the root schemas Definitions Container, these definition schemas can then be referenced and re-used elsewhere within the schema.

Schemas that reference a definition have a over the normal icon, and the type field shows the definition they are referencing.

"ISBN": {
    "$ref": "#/definitions/isbnType"
}

The UI will provide a list of existing definitions when the type field is dropped down and automatically build a reference is one is selected.