冒号的作用是引起读者的注意，由此引出后文。它的停顿意味要大雨逗号，甚至分号，但是弱于句号。冒号可以带有一种强制的、命令的意味，又可以显示一种言犹未尽的意味深长。
冒号的用法如下：
1. 引出直接引语、并列成分、同位语
(1) 引出直接引语。例如：
He added: "Yes, Miss Manette is going to be married." (注意 Yes是大写)
而英语更习惯用逗号引出直接引语，上句=He added, "Yes, ..."
但下句的冒号不能改为逗号，因为冒号迫使你去思考的意味相当明显。
Consider the words of John.K. Kennedy: "Ask not what your country can do fou you; ask what you can do for your country."(注意：Ask大写)
(2) 引出并列成分。例如：
The daily routine should at least be the following: twenty knee bends, fifty sits-up, fifteen leg lifts, and five minutes of running in place. (注意twenty 小写）
(3) 引出同位语的句子。例如：
My roommate is guilty of the seven deadly sins:gluttony and sloth. (注意：gluttony小写 )
2. 引出主语的解释或总结
Faith is like love: It can't be forced.
The sentence is poorly structured: it lacks both unity and coherense.
(注意：冒号后面的独立句，可以大写，也可以小写)
注意：不能滥用冒号。
首先，在动词和它的宾语或宾语补足语之间不能用冒号。例如：
Some important vitamins turned in vegetables are: vitamin A, thiamin, niacin and vitamin C.(应去掉冒号)
其次，在介词和它的并与之间不能用冒号。例如：
The area to be painted consisted of : three gable ends, sixteen windows, and a front porch.(应去掉冒号)
最后，在such as, including 或for example之后不能用冒号。