When to use a full stop (or "period" in American English)
什么时候用句号？
1. At the end of the sentence 句末
Thank you for your letter.
2. As a decimal point 作为小数点使用
2.5%, $9.99.
When to use a colon
什么时候用冒号？
1. To introduce a list 介绍一系列项目
You will need to bring the following: a waterproof jacket, a change of clothes, a battery-operated torch and some matches.
2. To introduce explanations 给出定义
There is one thing to remember: the nights can get cold, so bring a warm jacket.
3. To write the time 时间
The 10:40 train to London is late.
4. Between the title and subtitle of a book 书名的副标题
Shakespeare: The Complete Works
When to use a semi-colon in English
什么时候使用分号？
Semi-colons show a pause which is longer than a comma, but not as long as a full stop. Short clauses which are related in meaning can be separated by a comma. However, if the clauses are longer, you will probably need a semi-colon: 分号表达的是一个比逗号长句号短的停顿。有一些短句可以由逗号来断句，但是如果句子比较长的话，使用分号会比较合适。
We'll need to hold some meetings abroad with our suppliers; please could you check your availability in April.
1. To separate long items in a list在列表中区分较长的项目
Our writing course includes several components: correspondence, including
letters and emails; style and vocabulary choice; punctuation; layout and planning.
2. To give balance to sentences, or to link parallel sentences 使句子更平衡，或者连接并列句
We went out for the day; they stayed in.
When to use an apostrophe in English
什么时候使用单引号？
1. With an s to show possession 与s连用表示所属关系
The company's profits.
2. To show abbreviation 表示缩写
I don't like smoking. (= do not)