1793 分号有以下用法：

   1. 把没有连词连接而意思上都有联系的句子连接起来（可以用句号，但这时意思会被断开；也可用逗号，可能力量较弱不能把两句拉在一起；也可以用冒号，但现在很少这样用了）：

     It won’t last long ; it’s too weak .

     He is a clever fellow; even his enemy admits it.

     I love you; I worship you; I want you.

     He is content; he lives happily.

   2. 把内部包含有逗号的两个句子连在一起（这时不宜用逗号）：

     Dick is a generous, large-hearted person; but John, Mary and some of

   his friends are selfish people.

(Cf. Dick is a generous man, but John is a selfish fellow. )

 Alan ran his business carefully, methodically, and efficiently; and he was

   a great philanthropist, too.

He has three wives: one, who married him 20 years ago; a second, who

was a rich widow; the third, who has already married five times.

  3. 用在后面跟有逗号的连接副词之前：

     He studies hard; moreover, he has to work for his living.

     He has squandered all his wealth; therefore (或as a result), he has to beg his bread.

  4. 用在两个并列从句或两个短语之间（这时也可用逗号，但对比性较弱）：

     We know that country life is more quiet than city life; that it is more

 healthful; that it is happier.

     To work eight hours; to sleep eight hours; to do other things eight hours

 ---- that is the best way for man.

     That depends upon who do it; how they do it; and when .

5. 用在这类词前：

   We learn several subjects; such as (or e.g.) chemistry, and physics. (These are some of the subjects we learn.)

   We learn several subjects; that is (or i.e. viz, to wit, namely),

chemistry, physics, maths and biology.

      (These are all the subjects we learn.)

----- 在这种句子中也可用逗号或冒号代替分号：

We learn several subjects, namely chemistry, physics, and mathematics.

We learn several subjects : namely chemistry, physics, and mathematics.

We learn several subjects, namely chemistry, physics, and mathematics.

----- 但在下面这种句子中逗号、冒号或分号都不需要：

    We learn such subjects as chemistry and physics.

 （以上摘自《英语语法大全》，张道真编著，世界图书出版公司北京公司出版，2014年1月第1版）