Nexus point

When time travelling Daleks failed to effectively control the Roman emperor Caligula, the Elite Guard Dalek abandoned the mission whilst noting that there were other nexus points in human history. (COMIC: Empire of the Daleks)

Nexus points existed on other planets too, such as Bav and Teth, which were also attacked by the Daleks. (PROSE: The Dalek Problem)

The Seventh Doctor identified the Wenley Moor Affair as a crucial nexus-point in Earth's time stream from which a countless number of futures could be claimed resulting in near-endless divergent realities. (COMIC: Final Genesis)