Takt time.

Available production time divided by customer demand. A plant running 480 minutes a day against demand for 240 units has a takt of two minutes: one finished unit every two minutes, all day. It is not throughput. Throughput is what the line did, takt is what it has to do, and any station whose cycle time exceeds takt is the constraint whether or not it looks busy. In print-on-demand the number moves under you, because demand is the live order book rather than a forecast, so takt gets recomputed per shift instead of fixed once at line design. The word is German for a beat of time, and it reached production planning through 1930s aircraft assembly, as the interval at which an airframe was moved to the next station.