英语语法：119 Dashes Versus Colons

Grammar Girl here.

Today's topic is dashes.

Last week when I was speaking at the Field's End Writers Conference on Bainbridge Island, someone in the audience asked about dashes. When should she use a dash and how is it different from a colon¹?

Dashes and Drama

The difference between a colon and a dash is pretty subtle²: they can both serve to introduce a related element after the sentence, but a dash is a stronger and more informal mark than a colon. Think of a colon as part of the sentence that just ambles³ along. "Squiggly has two hobbies [and, now I'm going to tell you what they are, colon] cooking and bothering Aardvark."

A colon informs readers that something more is coming along. The words after a colon define⁴ or clarify what came before the colon. The two hobbies before the colon are defined⁵ after the colon as cooking and bothering Aardvark.

A dash also introduces extra material, but, well, a dash is quite a dramatic punctuation⁶ mark. A dashing young man is certainly not an ordinary young man, and if you're dashing off to the store, you're not just going to the store, you're going in a flurry.

A dash interrupts the flow of the sentence and tells the reader to get ready for some important or dramatic statement. If you added a dash to the "hobbies" sentence it would conceptually read something like this: "Squiggly has two hobbies [wait for it; wait for it; dash] cooking and bothering Aardvark." Wow!

Normally, you don't want to follow a dash with something boring or mundane⁷, so given that there isn't really anything exciting about Squiggly's hobbies, a dash may not be the best choice here. It would be a better choice if that sentence were part of a mystery novel where Aardvark has been attacked with chocolate pudding, and the police were investigating Squiggly's involvement. Then it could be a dramatic announcement that Squiggly's two hobbies are cooking and bothering Aardvark, and a dash would make more sense.

Dashes, Not Hyphens

And here's a very important rule about dashes: never, never, never use a hyphen in place of a dash. A hyphen is not a junior dash; it has its own completely separate use that I'll talk about some other time, but I can't talk about dashes without telling you not to use hyphens when you should use dashes. It's a common error.

If for some reason you can't insert the dash symbol, use two hyphens right next to each other: hyphen hyphen [--]. If you type two hyphens without any spaces on either side, most word processors will automatically⁸ convert⁹ them to an em dash. If you put spaces on both sides of the two hyphens, word processors will often automatically convert them to an en dash.

Em Dashes and En Dashes

Huh? What are these em dashes and en dashes of which I speak? An em dash is longer than an en dash. Those may seem like strange names, but they make sense when you realize that traditionally the em dash is as long as the typeset capital letter M and the en dash is as long as the typeset capital letter N.

The em dash is the kind of dash I was talking about before; it is the kind of dash you use in a sentence (1). When people say, “Use a dash,” they almost always mean the em dash.

The en dash is used much less frequently and usually only to indicate a range of inclusive¹⁰ numbers. You would use an en dash to write something like Squiggly will be on vacation December 2 to December 9, where the to between the dates is an en dash and indicates that Squiggly will not be in the office starting the 2nd of December and will return after the 9th of December (because an en dash indicates that the numbers are inclusive of the two dates).
Whether you are using the longer em dash in a sentence or the shorter en dash to indicate an inclusive range, there are no spaces between the dash and the words around it. This is actually a style choice, so you should consult a style guide if your company or teacher has one, but I recommend using no spaces.

Finally, you can find a complete transcript¹¹ of this podcast at the Grammar Girl section of QuickAndDirtyTips.com.

That's all. Thanks for listening.

 

1 colon   

n.冒号，结肠，直肠

参考例句：

• Here,too,the colon must be followed by a dash.这里也是一样，应当在冒号后加破折号。
• The colon is the locus of a large concentration of bacteria.结肠是大浓度的细菌所在地。

2 subtle   

adj.难于觉察或描述的，精巧的

参考例句：

• Her whole attitude had undergone a subtle change.她的整个态度发生了微妙的变化。
• There's a subtle hint of garlic in the sauce.调味汁里稍微有一点蒜味。

3 ambles   

v.（马）缓行( amble的第三人称单数 )；从容地走，漫步

参考例句：

• She ambles around the room, coming to rest before Dorothy again. 她在屋子里慢慢转悠，又走到多萝西的照片前站住了。 来自辞典例句

4 define   

vt.解释，下定义，阐述，限定，规定

参考例句：

• Please define the words.请解释这些字的意义。
• It's hard to define exactly what has changed.很难解释清楚到底发生了什么变化。

5 defined   

adj 定义的; 清晰的

参考例句：

• These categories are not well defined. 这些类别划分得不太明确。
• The powers of a judge are defined by law. 法官的权限是由法律规定的。

6 punctuation   

n.标点符号，标点法

参考例句：

• My son's punctuation is terrible.我儿子的标点符号很糟糕。
• A piece of writing without any punctuation is difficult to understand.一篇没有任何标点符号的文章是很难懂的。

7 mundane   

adj.平凡的；尘世的；宇宙的

参考例句：

• I hope I can get an interesting job and not something mundane.我希望我可以得到的是一份有趣的工作，而不是一份平凡无奇的。
• I find it humorous sometimes that even the most mundane occurrences can have an impact on our awareness.我发现生活有时挺诙谐的，即使是最平凡的事情也能影响我们的感知。

8 automatically   

adv.不加思索地，无意识地，自动地

参考例句：

• The machine cycles automatically.这台机器自动循环运转。
• She had automatically labelled the boys as troublemakers.她不假思索地认定这些男孩子是捣蛋鬼。

9 convert   

v.（在形式、状态、用途等方面）（使）改变

参考例句：

• I must convert sorrow into strength.我要化悲痛为力量。
• At what rate does the dollar convert into pounds?美元以什么汇率兑换成英镑？

10 inclusive   

adj.(of)包括的，包含的；范围广的

参考例句：

• The bill is inclusive of the food and lodging.账单包括吃、住费用。
• It's an all inclusive price;there is nothing extra to pay.这是一个包罗一切的价格，不需再额外付款了。

11 transcript   

n.抄本，誊本，副本，肄业证书

参考例句：

• A transcript of the tapes was presented as evidence in court.一份录音带的文字本作为证据被呈交法庭。
• They wouldn't let me have a transcript of the interview.他们拒绝给我一份采访的文字整理稿。