General speaking, it¡Çs about the relationship between virtual class(metaclass ) and Class. It¡Çs all in chapter 24. In Figure 24.2, Dave gives the relationship between object instance(a_guitar), its class(Guitar) and its metaclass(Guitar`). . Then in section ¡ÈClass and Module Definitions¡É , as we see in the code example, any class (for example, class Test) is a object instance of class Class. So I think Class is a metaclass of any class. Since Guitar` is a metaclass of Guitar, can I think Guitar` is a subclass of Class. If my understanding is right, I think it¡Çs better Dave can add this relationship in Figure 24.2 and make it clearer. Thanks in advance uncutstone -- Posted via http://www.ruby-forum.com/.