along

across, along, over, through

这些前置词均有“横过、穿过”之意。
across: 指“从……的一边到另一边”，强调横过，多与动态动词连用。
along: 指沿着一条直线在水平方向上运动。一般表动态，有时也与静态动词连用。
over: 常和动态动词连用，指“从……上面越过”或“横越”；表静态时，指“在彼处”。
through: 侧重从一端穿到另一端。

副词 along:

1. with a forward motion
   同义词：on
2. in accompaniment or as a companion
3. to a more advanced state
4. in addition (usually followed by `with')
5. in line with a length or direction (often followed by `by' or `beside')

1. Growing along the river are tall palm trees.
   沿着这条河生长的是高大的棕 树。
2. We bicycled along, singing loudly.
   我们骑着脚踏车前进，大声歌唱着。
3. We walked along the road.
   我们沿着路走。