StringReplace

StringReplace["string", s -> sp] replaces the string expression s by sp wherever it appears.

StringReplace["string", {s1 -> sp1, s2 -> sp2, ...}] replaces multiple patterns.

Examples

Replace a substring:

StringReplace["Hello World", "World" -> "Universe"]
(* "Hello Universe" *)

Multiple replacements:

StringReplace["cat and dog", {"cat" -> "dog", "dog" -> "cat"}]
(* "dog and cat" *)

Please visit the official Wolfram Language Reference for more details.