Space-time continuum

The space-time continuum was the term for the continuous set of coordinates created by the whole of space added to the whole of time. On Earth in the 20th century, the acceptance of Albert Einstein's Theory of Special Relativity demonstrated that time was not a constant. The concept of the space-time continuum — with time as an equal dimension — replaced the older idea of three spatial dimensions plus time. The First Doctor stated that the "fourth dimension", as humans understood it, was time. (TV: An Unearthly Child) "Continuum" was also used in relation to other phenomenon.

The Time Vortex was the structure of the space-time continuum. (PROSE: The Crystal Bucephalus)

N-Space, which was the prime universe according to the Doctor, was comprised of eleven dimensions, including those comprising the space-time continuum. (PROSE: Parasite) The Doctor's TARDIS herself stated that she was an eleven dimensional being that existed across all space and time, (TV: The Doctor's Wife) while the Fifth Doctor referred to the ship as having an internal continuum. (AUDIO: The Butcher of Brisbane)

The Black Guardian explained that converting the sixth segment of the Key to Time before the fifth would rip apart the space-time continuum by causing a temporal quake. (AUDIO: The Destroyer of Delights)

A TARDIS could not receive power from the Eye of Harmony outside of the normal continuum. (PROSE: State of Change)

By the time continuum of the 20th century, Gallifreyan civilization existed far in the past. (PROSE: Goth Opera)

The Interstitial Mass Transit System was formed by transdimensional tunnels which assaulted the space-time continuum on a level beyond human senses.

The Seventh Doctor stated that the Pythia's curse would send massive repercussions through the metareality of the space-time continuum. (PROSE: Transit)

Holes in the space-time continuum, rather than being outside of time and space, could lead to other universes. (PROSE: The Pit)