A parsec was a unit used to measure distance. It was used by the Time Lords. (TV: The Ribos Operation)

After landing on Karn, the Fourth Doctor claimed that the Time Lords had dragged his TARDIS 1000 parsecs off course. (TV: The Brain of Morbius)

While departing Traken on an initial course to Gallifrey, the Doctor instead opted to go to Earth which, as he claimed to Adric, was "one the way, more or less, give or take a parsec or two". (TV: Logopolis)

Aboard the Harmony and Redemption, River Song told Flemming to scan the whole parsec for the Doctor, unaware that she was standing next to the Twelfth Doctor. (TV: The Husbands of River Song)

Behind the scenes[]

In the real world, the parsec is a unit of length used in astronomy, equal to about 30.9 trillion kilometres (19.2 trillion miles) or 3.26 light-years.