* it doesn't do tail call optimisation unless you explicitly mark the self-call using by using recur (the lack of implicit TCO is a JVM limitation) * it doesn't use macros as much, although they are they're there and still used pretty often * it has language literals for the built-in data structures that look odd to other LISP'ers, e.g. {...} #{...} [...] * it's error messages are ecosystem dependent, e.g. Java stack traces for Clojure or and JS ones for ClojureScript