[f1shy]

Yes, of course I meant the basic S-exp syntax. They are indeed very different languages. The IMHO the biggest differences are scoping, and 1-Lisp and 2-Lisp; which makes different worlds.

[lispm]

all four now use lexical scope. Scheme also supports dynamic scope.

1-lisp or 2-lisp is also a difference, though all support lexical closures and function objects.

Racket now has a variant without s-expressions. That's also a huge difference.