coerce to a string
Major Section:  PROGRAMMING

(String x) coerces x to a string. If x is already a string, then it is returned unchanged; if x is a symbol, then its symbol-name is returned; and if x is a character, the corresponding one-character string is returned.

The guard for string requires its argument to be a string, a symbol, or a character.

String is a Common Lisp function. See any Common Lisp documentation for more information.