R4RS 6.4  (symbol? object)  ==>  boolean

Returns #T if OBJECT is a symbol, otherwise returns #F.

(symbol? 'foo)          ==>  #t
(symbol? (car '(a b)))  ==>  #t
(symbol? "bar")         ==>  #f
(symbol? 'nil)          ==>  #t
(symbol? '())           ==>  #f
(symbol? #f)            ==>  #f
