A rerun or repeat is a rebroadcast of an episode of a television or radio program.
History
Though not common practice in the 1960s, circumstances meant that the very first episode of Doctor Who, "An Unearthly Child", was also the first to be repeated. Due to the original airing being overshadowed by news of the assassination of John F. Kennedy the previous day, on Wednesday 27 November, the Programme Review board decided to repeat "An Unearthly Child" immediately before "The Cave of Skulls". This repeat, which was not shown on BBC One Northern Ireland, gained a significant number of viewers — 6.0 million.
The Evil of the Daleks was the first Doctor Who serial to be repeated in its entirety. This occurred between June and August 1968, when the serial was aired to fill the gap between seasons 5 and 6, with a two-week break between episodes three and four to accommodate the BBC's extended coverage of the Wimbledon tennis tournament. Unlike most reruns, the repeat was actually worked into the narrative of the series, by having the Second Doctor present the event to the new companion Zoe Heriot via a telepathic projector hidden behind one of the roundels of the console room. For the repeats, episode one had an added voice-over by Patrick Troughton and Wendy Padbury immediately after the opening title sequence referring back to the fact that this was being "shown" to Zoe.
In the run up to the start of Peter Davison's tenure as the Fifth Doctor, The Five Faces of Doctor Who was a season of repeats organised by John Nathan-Turner, broadcast on BBC Two on Monday to Thursday evenings and which began in November 1981, consisting of five four-part stories from the first four Doctors, including Logopolis as it featured the first on-screen appearance of the Fifth Doctor, and doing so justified the title of the season itself. A second season of repeats, titled Doctor Who and the Monsters, was broadcast on BBC One the following year.
Since 2005, episodes of the revived Doctor Who series are typically rerun on BBC Three or BBC Two in the week following their premiere on BBC One.