NST

例句：

1. 1. The NST is the shortest time between two events.
   NST是两个事件之间的最短时间。
2. 2. The NST is used to measure the distance between two points on a map.
   NST用于测量地图上两点之间的距离。
3. 3. The NST is also used to calculate the speed of an object moving at a constant velocity.
   NST还用于计算以恒定速度移动的对象的速度。