drop in的例子：
Drop in to see us any time.
隨便什麼時候順便來看看我們。
I" d like to drop in and see you sometime next week.
我想在下週什麼時候順便來看看你。
It"s improper to drop in on him so casually.
這樣冒冒失失去找他可不好。
Oh! I just drop in on him for a chat.
哦，我只是順便來和他聊聊天
drop by的例子：
I have to drop by the bank to get some money.
我得到銀行去取一下錢
Would you drop by when you are in town?
你來城裡就來玩好嗎?
I"ll drop by later to check on you.
等一下我會順道去看看你。
Only very close friends drop by unannounced.
只有非常親密的朋友才可能不請自來，
從上面的對比看，兩個片語的用法上的區別是drop in後面可以跟on，後接拜訪的人，而drop by一般不這麼使用。
另外，drop in含有臨時生出主意造訪的意思，造訪未經事先安排。而drop by沒有明確這層含義
drop in的例子：
Drop in to see us any time.
隨便什麼時候順便來看看我們。
I" d like to drop in and see you sometime next week.
我想在下週什麼時候順便來看看你。
It"s improper to drop in on him so casually.
這樣冒冒失失去找他可不好。
Oh! I just drop in on him for a chat.
哦，我只是順便來和他聊聊天
drop by的例子：
I have to drop by the bank to get some money.
我得到銀行去取一下錢
Would you drop by when you are in town?
你來城裡就來玩好嗎?
I"ll drop by later to check on you.
等一下我會順道去看看你。
Only very close friends drop by unannounced.
只有非常親密的朋友才可能不請自來，
從上面的對比看，兩個片語的用法上的區別是drop in後面可以跟on，後接拜訪的人，而drop by一般不這麼使用。
另外，drop in含有臨時生出主意造訪的意思，造訪未經事先安排。而drop by沒有明確這層含義