▲along 表示“沿着”时，其后所接名词通常为 road, river, corridor, line, coast 等形状狭长的东西。如：
The ship cruised along the shore. 那艘船沿着海岸巡航。
Many fishermen own cabins along the lake. 许多渔民在盐湖岸边有小屋。
We continued along the path until we came to the river. 我们沿着小路一直走到河边。
We all admired the beautiful view while driving along the coast. 我们沿海岸行驶时，大家都对那美丽的景色赞叹不已。
▲down 表示“沿着”时，通常指向下、向远处之意。如：
He fell down the stairs. 他从楼梯上摔下来。
Tears ran down her face. 眼泪顺着她的脸流了下来。
We must row down the stream. 我必须顺流往下划。
He was walking down the street. 他沿着街道往前走去。
Pass down the bus and make room for more passengers. 往车厢里面走，让更多的乘客上车。
▲up 表示“沿着”时，通常指向上、向近处之意。如：
The cat climbed up the tree. 那只猫爬上树。
She carried the bag up the stairs. 她把袋子扛上了楼梯。
▲表示沿着道路等时，用along, up, down 都可以，区别很小，几乎可以互换：
The nearest post office is about half a mile along [up, down] the road. 最近的邮局要沿着这条路大约走半英里。
但有时也会有些细微区别：
We walked up the river for about half an hour. 我们沿河走了大约半小时。(可能是往上游走)
We walked down the river for about half an hour. 我们沿河走了大约半小时。(可能是往下游走)
We walked along the river for about half an hour. 我们沿河走了大约半小时。(不区分上游和下游)