In music, a theme, also frequently called a motif, is the initial melody. After the principal theme or motif is announced, a second voice takes up the second melody, called a countertheme or countermotif. In a three-part fugue, the principal theme is announced three times in three different voices -- soprano, alto, bass -- or some variation of that. In a four-part fugue, the principal motif is announced four times. A leitmotif is a theme associated with a particular character in a play.

In literature, a theme is the main idea of the story, or the message the author is conveying. This message is usually about life, society or human nature. Not all stories have themes (they are optional in escape fiction).

General rules for stating a theme are:

Use complete sentences.
Make a point about a specific topic. For example, the statements that the theme is love is incorrect- what about love?
Do not use names. Instead use one, a person, people, etc.
Do not use absolutes such as: always, never, everyone, must, everybody, etc.
Do not use cliches, e.g. Crime doesn't pay.
Do not give lessons or morals.
A theme must be based on and supported by the entire story.