Rel
A rel was a Dalek unit of measurement, principally of time.
The Daleks used rels for time measurement. (BFA: The Genocide Machine, The Mutant Phase, DW: Doomsday) One rel was slightly longer than a second. (DW: Evolution of the Daleks)
In other contexts, it was a unit of speed, where presumably rel is short for some standard unit of distance per rel. (TV21: Plague of Death) A rel was also used as a unit to measure hydroelectric energy, not to be confused for a vep, the unit used for artificial sunlight (DWA: The Dalek Book) When the New Dalek Empire tried to destroy the universe with the reality bomb using the Medusa Cascade, they counted down from 10 rels until their attempt to use it. (DW: Journey's End)
Behind the scenes
The word Rel first appeared in the non-canonical movie Daleks' Invasion Earth 2150 A.D., before appearing in early Doctor Who comics.
