Space

Space was a word used to refer to two different concepts relating to the universe. One referred to dimensions: space being described by Susan Foreman as the fifth dimension. (TV: "An Unearthly Child") Space was also defined as the vacuum in the universe, outside of a planetary body's atmosphere. This was often known as "outer space". (TV: The Runaway Bride)

Space/vacuum exposure
Krynoid pods survived exposure to the vacuum of space by hibernating during voyages through space. (TV: The Seeds of Doom)

Wirrn lived in and travelled through space. They could live without fresh oxygen for several years, but their breeding colonies were terrestrial. (TV: The Ark in Space)

The Rutan Host could travel through space without any effects. (PROSE: Shakedown)