Serial (radio and television)
In television and radio programming, a serial 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 full run of the series, which distinguishes them from traditional episodic television that relies on more stand-alone episodes. Worldwide, the soap opera is the most prominent form of serial dramatic programming.
Steven Bochco
Prior to "Hill Street Blues" it was rare for American straight drama series to have story arcs, i.e. several stories running over many episodes (with the exception of prime time soap operas such as "Dallas"). It was also rare to have a large regular cast. The structure of the modern "ensemble" television drama can be traced to Bochco, who many regard as having changed the "language" of television drama.