http://hl7.org/fhir/StructureDefinition/11179-objectClassProperty|5.2.0

A quality common to all members of an object class. A property may be any feature that humans naturally use to distinguish one individual object from another. It is the human perception of a single quality of an object class in the real world. It is conceptual and thus has no particular associated means of representation by which the property can be communicated.