Parentheses圆括号（）
（1） 在一句子中插入字或语句，可使用圚括号，正如用dashes破折号一样，但用折号会突出插入句的意思，而用圆括号则会令插入句不明显，只作补充资料。一般来说，在一篇文章中，不要使用太多圆括号，否则，会分散了读者的注意力。
用破折号：
The books and journals – and tapes, filmstrips, even the people you want to interview – are all too often unavailable when you are ready.
用圆括号：
The books and journals (and tapes, filmstrips, even the people you want to interview) are all too often unavailable when you are ready.
（2） 用圆括号来阐明前述资料：
例子：
Our linguistic habits (how we listen, talk, and think) must be improved.
（3） 在列点的句子中，将数字或字母放入圆括号内：
例子：
Boston and San Francisco were compared in terms of (1) location, (2) cultural advantages, (3) work opportunities, and (4) moral values of people.
（4） 在商业书信中，用圆括号附入数目字，以重复一个详细数字写法：
例子：
The monthly rent is five thousand & fifty dollars ($5,050).
We confirmed that the order of eighty (80) gross was shipped yesterday.
注意：圆括号内的资料不应该影响到原来句子的结构或标点符号，如果标点正常是出现在圆括号开始的地方，则加入圆括号后，原来的标点应紧接着圆括号之后。
例子：
Regardless of what you hear (and you may hear many lies), do not believe anything unless it appears in our regular newsletter.
Brackets 括号 [ ]
（1）在引文中插入的字句，使用括号封入，以作阐明或解释引述资料：
例子：
“He [Hermes] is often portrayed as sly and cunning, both in word and deed, a trickster giving to cheating and lying.” Philip Mayerson
（2）在圆括号中插入简短资料时，可用括号封入：
例子：
From that point on, Thomas Parker simply disappears. (His death [c. 1441] is unrecorded officially, but a gravestone marker is mentioned in a 1640 parish report.)