GMAT考试，语法题的部分经常会出现考标点符号的，而常用的标点符号有：Semicolons分号、Colons冒号、Commas逗号、Parentheses括号、Dashes破折号、Hyphens连字号、Ellipsis省略号和Quotation marks引号。上期天道留学小编为大家整理的是有关分号和冒号的知识点，这期为大家整理的是逗号和括号的用法。

　　1. Dashes 破折号(―)

　　a. Use a dash to link two parts of a sentence.

　　例句：

　　Okay: Always buckle your seat belt; it's the law.

　　Stronger: Always buckle your seat belt―it’s the law.

　　b. Use a pair of dashes to emphasize by-the-way, parenthetical expressions.

　　例句：

　　*My grandmother bought me a puppy―an adorable little bulldog!―for my birthday.

　　*I’ve lived in Portland―the one in Oregon, not Maine―all my life.

　　c. Use a dash to set off a long appositive (a description of who or what the subject is) or an appositive with lots of commas.

　　例句：My best friends―Amani, Catherine, Erin, Kai, and Lola―are here.

　　d. Use a dash in dialogue to show hesitation or a break in the flow of the sentence.

　　例句：Esperanza said, “I definitely studied enough for the test―or I think I studied enough―I probably studied nearly enough―well, I hope I studied enough.”

　　e. Use a dash to sum up a list or idea.

　　2. Hyphens连字号(-)

　　a. Use a hyphen with some prefixes, especially all-, co-, ex-, great-, numbers, and capital letters.

　　b. Use a hyphen when a word would be confusing or hard to read without it.

　　Should you use parentheses, commas, or dashes?

　　Think of parentheses as hiding information (de-emphasizing it) while dashes highlight information―emphasizing it. Think of commas as being matter-of- fact, neither highlighting nor hiding information. If the parenthetical information is very closely related to the sentence, commas are usually better.

　　例如，

　　词组：shell-like

　　句子： Ann recovered from the flu and re-covered her living room chair. 两个recovered容易混淆，因此第二个加上hyphen以作区分;第一个recovered表示身体恢复了，第二个re-covered表示找回椅子了。

　　c. Use a hyphen with double last names.

　　d. Use hyphens (or slashes) with dates.日期表达格式：月-日-年

　　e. Use a hyphen with compound numbers from 21 to 99.

　　f. Use a hyphen with scores.

　　g. Use hyphen in compound adjectives if they come before the noun they describe. 例如，the 15-year-old girl

　　h. Use a hyphen to mean through.

　　例如， page 16-24

　　i. Use hyphen to spell out words.

　　例句：My name is Kacey, K-a-c-e-y.

　　j. Use hyphen to show faltering speech.

　　k. Use hyphen in some compound words (two or more separate words that we think of as one unit).

　　l. Use hyphens for hyphenating word. 这种情况就是手写书信的时候会遇到：字写满了一行，已经到纸的边缘了，但是最后一个单词没法写完，用hyphen连起来，再另起新的一行把单词剩下部分补上。