An alter ego (from Latin, "other I") is another self — a second personality within a person. It is also called leading a double life. The term "alter ego" was first used in the 19th century. It was inventory by psychologists in talking about dissociative identity disorder.
For example, in The Strange Case of Dr Jekyll and Mr Hyde, Mr. Hyde was Dr. Jekyll's evil alter ego (same person, different personalities).
The term is also used in popular fiction, like comic books, for the secret identity of a superhero, vigilante, or crimefighter. The character would do this so people won't know that he or she is fighting crime. Examples of characters using alter egos include:
Sometimes an artist uses an alter ego, like: