Second run

A rerun or repeat is a rebroadcast of an episode of a radio or television program. There are two types of reruns – those that occur during a hiatus, and those that occur when a program is syndicated. Reruns can also be, as the case with more popular shows, when a show is aired outside of its timeslot (for example, in the afternoon).

In the United Kingdom, the word "repeat" refers only to a single episode; "rerun" or "rerunning" is the preferred term for an entire series/season. A "Repeat" is a single episode of a series that is broadcast outside its original timeslot on the same channel/network. The episode is usually the "repeat" of the scheduled episode that was broadcast in the original timeslot earlier the previous week. It allows viewers who weren't able to watch the show in its timeslot to catch-up before the next episode is broadcast. The term "rerun" can also be used in some respects as a synonym for reprint, the equivalent term for print items; this is especially true for print items that are part of ongoing series (such as comic strips; Peanuts, for instance, has been in reruns since the retirement and death of creator Charles M. Schulz). In South Africa, reruns of the daily soap opera 7de Laan, and others, are called an Omnibus. The Omnibus is a weekly rerun that is broadcast on a Sunday afternoon on the original channel/network. It only broadcasts the past week's episodes back-to-back.

When used to refer to the rebroadcast of a single episode, Lucille Ball and Desi Arnaz are generally credited as the inventors of the rerun; it was first utilized for the American television series I Love Lucy (1951–57) during Ball's pregnancy.

In the United States, most television shows from the late 1940s and early 1950s were performed live, and in many cases they were never recorded. However, television networks in the United States began making kinescope recordings of shows broadcast live from the East Coast. This allowed the show to be broadcast later for the West Coast. These kinescopes, along with pre-filmed shows, and later, videotape, paved the way for extensive reruns of syndicated television series.

...
Wikipedia