轨

例句：

1. 1. The train tracks are straight as an arrow.
   火车轨道直如箭。
2. 2. The path of the river follows a natural curve.
   河流的路径自然弯曲。
3. 3. The satellite's trajectory is carefully monitored by scientists.
   卫星的轨迹由科学家仔细监控。