n.速度；迅速；速率
The velocity of sound in water is more than four times that in air. 声音在水中的速度是在空气中的速度的4倍多。
Gazelles can move with astonishing velocity. 羚羊跑起来速度惊人。
The velocity of light is about 186,000 miles per second. 光速大约是每秒十八万六千英里。
