API Reference > imodeljs-frontend > QuantityFormatting > QuantityTypeDefinition > key key Readonly key: string String used as a key to look up the quantity type. If defining a CustomQuantityTypeDefinition the QuantityTypeKey should match the QuantityTypeArg. Defined in core/frontend/src/quantity-formatting/QuantityFormatter.ts Line 118 Last Updated: 12 June, 2024