`  == Definition? == Sorry to be annoying, but is there any chance of putting a definition in the lead? All this deep discussion is very interesting, but in the first few paragraphs there should be something like ``A spinor is a....`` or ``Spinors are members of ....``. The best that the article can manage is to tell me that spinors are group homomorphisms (because that is what representations are defined to be in wikipedia). I am pretty certain spinors aren't defined as members of a group of homomorphisms, so how about a definition, one that doesn't begin ``You can think of...`` or some such weasel phrase? This is a real concern for me and I am sure many others reading an article like this. It may be that if you *know* what is meant you can interpret it. At the moment what is there is neither a definition a lay person can understand nor in internal terms a pedantically correct one.   `