Plea has come to mean in the popular vernacular the assertion by a criminal defendant whether he is guilty or not guilty. More generally, a plea is simply an answer to a claim made by someone in a civil or criminal case under common law.

The concept of the plea is one of the major differences between criminal procedure under common law and procedure under civil law. Under common law, a plea of guilty by the defendant causes a jury trial to be waived and the criminal process to proceed to sentencing. This produces a system under American law known as plea bargaining[?].

Under civil law, there is no concept of a plea. A confession by the defendant is treated like any other piece of evidence, and a full confession does not prevent a full trial from occurring or absolve the prosecution from presenting a case.