src/Pure/Tools/class_package.ML

 val parse_arity =
   (P.xname --| P.$$$ "::" -- P.!!! P.arity)
     >> (fn (tyco, (asorts, sort)) => ((tyco, asorts), sort));
 
 val classP =
-  OuterSyntax.command classK "define operational type class" K.thy_decl (
+  OuterSyntax.command classK "define type class" K.thy_decl (
     P.name --| P.$$$ "="
     -- (
       class_subP --| P.$$$ "+" -- class_bodyP
       || class_subP >> rpair []
       || class_bodyP >> pair [])