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)
Along 當副詞用時意為「向前；一道，一起 (together with)」。例如：
- They were just walking along, chatting. (他們就這樣一邊 (向前) 走著一邊閒聊)
- Why don’t you take him along with you to the party? (你為什麼不帶他一起去參加派對呢？)
- Ramos visited us and brought his sister along. (羅慕斯帶著他妹妹一起來看我們)
- Can I bring the children along? (我可以帶著孩子們一起來嗎？)
- Kent was arrested along with nine other men. (肯特和另外九名男子一起被捕)
Alongside 當介系詞用時意為「在…旁邊 (next to)；和…並排靠攏著；和…在一起 (together with)」。例如：
- His boat pulled up alongside the dock. (他的船停靠在碼頭旁)
- A sports car pulled up alongside mine. (一部跑車停在我的車旁)
- A sports car drove up alongside me. (一部跑車開到我的身旁)
- The new server will be used alongside existing machines. (這台新伺服器將跟現有的機器一起使用)
- Most of the employees were willing to work alongside the new team. (大多數員工都願意和這個新團隊一起工作)
Alongside 當副詞用時意為「在旁邊；並排靠攏著」。例如：
- Jimmy was riding on a donkey with his father walking alongside. (吉米騎在驢子上，而他父親在一旁走著)
- A sports car pulled up alongside. (一部跑車停在旁邊)