noun
group velocity
Technical term in physics and fiber optics; the speed at which the envelope of a wave packet travels.
光ファイバーでは、群速度が信号の伝搬速度を決める。
In optical fibers, the group velocity determines the signal propagation speed.
Compound of 群 (group) and 速度 (velocity), a direct translation of the English term 'group velocity'.