That&#x27;s only the syntax of s-expressions - a data format.<p>The Lisp syntax is defined on top of s-expressions.<p>For example Common Lisp has a CASE operator. That&#x27;s the EBNF syntax:<p><pre><code>    case keyform {normal-clause}* [otherwise-clause] =&gt; result*
    normal-clause::= (keys form*) 
    otherwise-clause::= ({otherwise | t} form*) 
</code></pre>
An example:<p><pre><code>    (case id
      (10 (foo))
      (20 (foo) (bar))
      (otherwise (baz)))
</code></pre>
The expressions are written using s-expressions as data. But still there is structure in those s-expressions, described by the EBNF syntax of CASE.<p>Every special operator and every macro provides syntax. Since users can write macros themselves, everybody can extend the syntax. On top of s-expressions.