A good way of getting at this is to call things at runtime "classes" or "tags" to make it apparent that their discrimination happens at runtime, not compile-tim

A good way of getting at this is to call things at runtime "classes" or "tags" to make it apparent that their discrimination happens at runtime, not compile-time. The problem is that if you call both things types, you quickly run into a situation where you are essentially talking about different concepts entirely. Note that most sum-types are implemented by having a runtime tag on which you can discriminate.