I was working on Acquire Spanish, my universal language course. Specifically, I was trying to to come up with a term that defined the tipping point when the language habit kicks in.
I thought of ‘critical mass’, ‘combustion point’, ‘flash point’, ‘auto-ignition’, ‘rolling momentum’, or ‘overcoming the force of friction’. I even tried to co-opt Newton’s first law which says that an object—whether moving or stationary—tends to remain in that state.
But my best word picture, one that does not employ the jargon of science, is simply to describe it as the moment when language activity becomes self-sustaining.