Keywords are similar to symbols. The main difference is that keywords are self-evaluating and therefore do not need to be quoted in expressions. They are used mainly for specifying keyword arguments.
[75] keyword = identifier:
A keyword is a single token; therefore, no whitespace is allowed between the identifier and the :. The : is not considered part of the name of the keyword.
(keyword? obj)
Returns #t if obj is a keyword, and otherwise returns #f.
(keyword->string keyword)
Returns the name of keyword as a string.
EXAMPLE 44
(keyword->string Argentina:) ==> "Argentina"
(string->keyword string)
Returns the keyword whose name is string.
EXAMPLE 45
(string->keyword "foobar") ==> foobar: