Hello, I am trying to learn haskell , but i am struggling with types , its been around 7 days , it will be very kind if some explain it why this error , i think this is the only stumbling block . I am looking for the comparison on why similar code works , while other code not . I get this error on ghci : {- `a' is not applied to enough type arguments Expected kind `*', but `a' has kind `* -> *' In the type `SS a' In the type `(Monad a) => {Monad (SS a)}' In the instance declaration for `Monad (SS a)' -} Here is the very small code with comments: data SS a = SS a Int data Maybe1 a = Nothing1 | Just1 a instance Monad Maybe1 where (Just1 x) >>= f = f x --^^ this loads fine in ghci -- where as this instance (Monad a)=> Monad (SS a) where (SS x y) >>= f = f (x y) --^^ does not work , so whats the difference , both have type parameters -- something similar works like this : instance (Eq a)=>Eq (SS a) where (SS x y) == (SS b c) = (y == c) && (x == b) Thanks