Along 和 alongside 皆可當介系詞和副詞用，但兩者的用法並不相同、遑論互換。所以，在應使用 along 的地方，若使用 alongside 來替代，不是文法錯誤，就是意思有別，反之亦然。
Along 當介系詞用時意為「沿著，順著，循著」。例如：
- They walked along the beach collecting small crabs in a bucket. (他們沿著海灘走，拿著桶子一路撿拾小螃蟹)
- A black cat was walking along the top of the fence. (一隻黑貓在籬笆上頭走著)
- We went for a romantic walk along the river yesterday. (我們昨天沿著河邊浪漫地散步)
- Cars were parked all along the riverbank. (河岸沿途停滿了汽車)
- Somewhere along this road there’s a bookstore. (順著這條路走，路邊有一家書店)
Somewhere alongside this road there’s a bookstore. (在這條路附近的某個地方有一家書店)