of s-expressions. Lisp has an additional layer of syntax on top of s-expressions.

For example the DEFINE-CONDITION operator has this syntax:

  define-condition name (parent-type*) ({slot-spec}*) option* => name

  slot-spec::= slot-name | (slot-name slot-option) 

  slot-option::= [[{:reader symbol}* |  
                   {:writer function-name}* |  
                   {:accessor symbol}* |  
                   {:allocation allocation-type} |  
                   {:initarg symbol}* |  
                   {:initform form} |  
                   {:type type-specifier} ]] 

  option::= [[(:default-initargs . initarg-list) |  
              (:documentation string) |  
              (:report report-name) ]] 

  function-name::= {symbol | (setf symbol)} 

  allocation-type::= :instance | :class 

  report-name::= string | symbol | lambda expression