標點符號（punctuation marks）看似簡單，但很多同學仍然沒有掌握好如何使用它們；因此，今天將會跟同學討論一下如何運用一些常見的punctuation marks。
Full-stop （.）
Full-stop 用在表示句子的完整性（completeness）；倘若同學將full-stop 誤放在不完整的句子後，那句子將會成為一句fragment。例如：
E.g.1︰If you are free tomorrow night. Let's go to watch a movie. (×)
在這例子中，full-stop被放在「if you are free tomorrow night」後；由於句中欠缺main verb（主動詞），句子並不完整，亦因此full-stop被錯置。
Comma沒停頓以外文法功用
Comma（,）
Comma 主要用來顯示停頓位（pause）；它並沒有其他任何文法上的功用；很多時候，同學錯在用comma來連接完整句子；以下是常見的錯誤：
E.g. 2︰Many people dream of having a lot of money, however, they often fail to see money can sometimes create more problems. （×）
把comma 放置在兩句完整的句子中是同學常犯的錯，因為comma根本不能用來連接句子。
Semi-colon（;）
與comma不同，semi-colon 可以用來連接完整句子；因此example 2 可被改寫為：
E.g.3: Many people dream of having a lot of money; however, they often fail to see money can sometimes create more problems. (??)
從以上example 3 中，semi-colon 就像連接詞conjunctions（such as and, or, but etc.）一樣；可用來連接句子。
Colon列舉重點 讀者易留意
Colon（:）
雖然同學們未必會時常運用colon，但在一個情況中，同學有機會用得上colon--那就是當同學運用listing technique（列舉）時。當同學們有一連串重點想更容易被讀者留意到時，很多時候他們會用列舉的方式把重點顯示出來。以下是一簡單例子：
E.g. 4
To protect your computers from being hacked, you should:
．install the operation system updates
．use a firewall
．avoid saving your passwords on your computers.
E.g. 5
To protect your computers from being hacked, you should: (1) install the operation system updates, (2) use a firewall, and (3) avoid saving passwords on your computers.
從以上的例子，你可見到colon 會用在帶出列舉項目，無論例舉的形式是vertical list還是horizontal list。
Exercise
Fill in the blanks by using the correct punctuation mark.
A lot of people believe that learning a second language s should start at pre-schools (____) however, more evidence now demonstrates that older children are found to be learning a second language better than younger children.
Answers:
A lot of people believe that learning a second language should start at pre-schools (;) however, more evidence now demonstrates that older children are found to be learning a second language better than younger children. [semi-colon]
A lot of people believe that learning a second language should start at pre-schools (.) However, more evidence now demonstrates that older children are found to be learning a second language better than younger children. [Full-stop]
■Dr. A. Chan