In television and radio programming, a serial is a show that has a continuing plot that unfolds in a sequential episode-by-episode fashion. Serials typically follow main story arcs that span entire television seasons or even the complete run of the series, and sometimes spinoffs, which distinguishes them from episodic television that relies on more stand-alone episodes. Worldwide, the soap opera is the most prominent form of serial dramatic programming. In the UK the serial began as a direct adaptations of well known literary works, usually consisting of a small number of episodes.