Letters are important means of communication. Generally speaking, there are two types of letters, business letters and personal letters.

信函是交流的重要手段。一般而言，有两种信函形式，商务信函和私人信函。

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Generally speaking, letters may be classified into two categories: one is letters to relatives and friends, called personal letters, the other is business letters.

书信一般分为两大类，一类是写给亲朋好友的信件，称为私人信函，另一类则是事务信函（包括公函）。

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Generally speaking, letters may be classified into two categories: one is letters to relatives and friends, called personal letters, the other is business letters.

书信一般分为两大类，一类是写给亲朋好友的信件，称为私人信函，另一类则是事务信函（包括公函）。

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