Role-playing or roleplaying is the changing of one's behaviour to assume a role, either unconsciously to fill a social role, or consciously to act out an adopted role. While the Oxford English Dictionary offers a definition of role-playing as "the changing of one's behaviour to fulfill a social role", in the field of psychology, the term is used more loosely in four senses:

• To refer to the playing of roles generally such as in a theatre, or educational setting;
• To refer to taking a role of a character or person and acting it out with a partner taking someone else's role, often involving different genres of practice;
• To refer to a wide range of games including role-playing video game (RPG), play-by-mail games and more;
• To refer specifically to role-playing games.