trajectories
n. 轨迹；轨道线（trajectory 的复数形式）
例句
When that separation lasts for a period of time, the two populations are able to evolve along different trajectories.
当这种分离持续一段时间后，这两个种群能够沿着不同的轨迹进化。
Trajectories, thank goodness, are almost never three-dimensional.
轨迹，感谢上帝，基本上永远不是三维的。
Now comes my last part, and that is, how does air drag influence trajectories?
现在是最后一部分，就是，空气阻力如何影响轨道？
