The term comes from Vernor Vinge, who argued in 1993 that superhuman intelligence would arrive within thirty years and end the human era as we know it. He borrowed it from physics. At the edge of a black hole the normal rules stop working, and Vinge thought the world after superhuman intelligence would be just as impossible to see from here. Ray Kurzweil later gave it a date, 2045.
Both versions describe a threshold you would notice. The leaders of frontier AI labs now describe something slower: Sam Altman’s “gentle singularity” is a takeoff that has already started and feels ordinary while you live through it. That difference matters for planning. A single event can be prepared for. A slope is easy to miss until the gap it opens is already large.
The useful test is practical. Ask where machines in your organisation already produce work faster than your people can check and understand it. That gap is the first measurable sign of a takeoff, whatever anyone calls it.