這是一位朋友在本公眾號後臺的點題，原話是：
你好，through和by後面跟方式、方法時有什麼區別？
對於這樣的問題，我的第一反應是去查詞典。要說用，我能用對，但要說出道理來，還是得看看歷代先賢是怎麼說的。查詞結果如下：
by表示方式方法：
《新牛津英漢雙解大詞典》：
[often with verbal noun]indicating the means of achieving somethingmalaria can be controlled by attacking the parasite.substantiating their opinions by the use of precise textual reference.they plan to provide further working capital by means of borrowing.indicating the means of transport selected for a journey ［表示旅行所用的交通工具］
the cost of travelling by bus.
乘汽車旅行的花費。
travelling by road to Aylsham.
乘汽車去艾爾舍姆。
《朗文當代英語詞典》：
2 MEANS/METHOD: used to say what means or method someone uses to do something
--You can reserve the tickets by phone.
--Send it by airmail.
--Some customers prefer to pay by cheque.
by car/train/bus/taxi etc
--They travelled to Chicago by train.
by air/sea/land/road/rail etc
--All supplies are transported by air.
by doing sth
She earns her living by selling insurance.
--He was taken from his home by force.
由上可見，基本上by就是方式方法、所用工具，尤其是交通工具。
through表示方式方法：
《新牛津英漢雙解大詞典》：
by means of (an intermediary or agent)seeking justice through the proper channels.by means of a particular method, service, person etc
--She got her first job through an employment agency.
--a success that was achieved through co-operative effort and wise leadership
--I heard about it through a friend.
由上面的釋義對比我們可以看出：
through主要解釋為「通過」（某一管道或中間人）。
比如，「通過一位朋友，以口頭的形式傳達消息」，就是：
send a message by word of mouth through a friend.
這就是by和through表示「方式方法」的時候的主要區別。
當然，很多時候如果是by doing sth.，也可以寫成through doing sth.，這是沒什麼問題的。
這其中的道理，其實不難理解。我們都知道，by和through本來並不單單指方式方法，它們的基本意思分別是by「在……旁邊」，through「通過（某事物內部）」。這樣就不難理解了，在表示方式方法的時候，by是旁邊有東西可用，就拿起來用，好比拿來主義；through是看到有一管道，就通過此管道去達成目的。
differencebetween.com對by和through的用法區別有一句相當精到的總結：
while the preposition by is mostly used when referring to a means of something, the preposition through is used in relation to a process.
至於說via，這是一個比較正式的單詞，可以在正式文體（學術文章、法律條文、公司財報、政府文書等）中替代through，但如果是through doing sth.，則through不可替換成via。
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