Time

Time is the dimension through which space-time vessels travel. The Web of Time governs order within this realm.

Explanations of time
Time was one of the five dimensions described by Susan Foreman and from which she derived the name TARDIS, which she came up with herself. (DW: An Unearthly Child) While Susan described time as a dimension, the Master (in the guise of "Professor Thascales") described time as made up of particles, known as chronons. (DW: The Time Monster)