The word "melodrama" comes from the Greek word for song "melody", combined with "drama". Music is used to increase the emotional response or to suggest characters. There is a tidy structure or formula to melodrama: a villain poses a threat, the hero escapes the threat (or rescues the heroine) and there is a happy ending. In melodrama there is a constructed world of connotations.
A melodrama in a more neutral and technical sense of the term is a play, film, or other work in which plot and action are emphasized in comparison to the more character-driven emphasis within a drama. Melodramas can be distinguished from tragedy by the fact that they are open to having a happy ending.
According to Michael Booth in his classic study English Melodrama the Victorian stage melodrama featured a limited number of stock characters: the hero, the villain, the heroine, an old man, an old woman, a comic man and a comic woman engaged in a sensational plot featuring themes of Love and Murder. Often the good but not very clever hero is duped by a scheming villain, who has eyes on the damsel in distress until fate intervenes at the end to ensure the triumph of good over evil.