A conceptual property cannot be deleted if one of the three following cases arise:
The software engineer has no authorities over the property.
The property has already been assigned to a conceptual entity or to a relationship. You can delete a property assigned to an entity or to a relationship using the dialog box for modifying the properties assigned to an object.
The conceptual property is attached to another application area (in this case, it will just be de-attached from the current application area).