英语语法：15 I.e. Versus E.g.

Grammar Girl here.

This episode is a new and improved version of i.e. versus¹ e.g.

Misusing² these two abbreviations is one of the top five mistakes I used to see when editing technical documents. There's so much confusion that in some of the drafts I got back from clients they had actually crossed out the right abbreviation and replaced it with the wrong one. I just had to laugh.

I.e. and e.g. are both abbreviations for Latin terms. I.e. stands for id est and means roughly "that is." E.g. stands for exempli gratia, which means “for example.” "Great. Latin," you're probably thinking. "How am I supposed to remember that?”

But by now, I'm sure you know that I'm not going to ask you to remember Latin. I'm going to give you a memory trick! So here's how I remember the difference. Forget about i.e. standing³ for "that is" or whatever it really means in Latin. From now on, i.e., which starts with i, means “in other words,” and e.g., which starts with e, means “for example.” I = in other words. E= example.

A few listeners have also written in to say that they remember the difference between i.e. and e.g. by imagining that i.e. means “in essence,” and e.g. sounds like “egg sample,” and those are good memory tricks too.

So now that you have a few tricks for remembering what the abbreviations mean, let's think about how to use them in a sentence.

E.g. means “for example,” so you use it to introduce an example: I like card games, e.g., bridge and crazy eights. Because I used e.g., you know that I have provided a list of examples of card games that I like. It's not a finite list of all card games I like; it's just a few examples.

On the other hand, i.e. means “in other words,” so you use it to introduce a further clarification: I like to play cards, i.e., bridge and crazy eights. Because I used i.e., which introduces a clarification, you know that these are the only card games that I enjoy.

Here are two more examples:

Squiggly loves watching old cartoons (e.g., DuckTales and Tugboat Mickey). The words following e.g. are examples, so you know that these are just some of the old cartoons that Squiggly enjoys.

Squiggly loves watching Donald Duck's nephews (i.e., Huey, Dewey, and Louie). The words following i.e. provide clarification: they tell you the names of Donald Duck's three nephews.

An important point is that if I've failed, and you're still confused about when to use each abbreviation, you can always just write out the words "for example" or "in other words." There's no rule that says you have to use the abbreviations.

Here are a few other things about i.e. and e.g. Don't italicize them; even though they are abbreviations for Latin words, they've been used for so long that they're considered a standard part of the English language. Also, remember that they are abbreviations, so there is always a period after each letter, and yet, despite the fact that they are abbreviations, there is no space in the middle.

Also, I always put a comma after i.e. and e.g. I've noticed that my spell checker always freaks out and wants me to remove the comma, but five out of six style guides recommend the comma. Seriously. I got so engrossed⁴ in the question of whether or not a comma is required after i.e. and e.g. that I made a  table for the web site summarizing the opinions of six different style guides.

Nevertheless, even though I prefer the comma and have sources to back me up, they almost all use hedge words like “usually” and “preferred.” I've also been told that the commas are used less frequently in Britain, and the only style guide I found that advised against commas was Fowler's Modern English Usage, which has its roots in British English. The bottom line is that in American English, I recommend using a comma after i.e. and e.g. You could probably make an argument for leaving it out in some cases, but do so at your own risk. My personal rule is to use a comma every time.

Finally, I tend to reserve i.e. and e.g. to introduce parenthetical statements, but it's also perfectly⁵ fine to use i.e. and e.g. in other ways. You can put a comma before them, or if you use them to introduce a complete sentence that follows after another complete sentence, you can put a semicolon before them. You can even put an em dash before i.e. and e.g. if you are using them to introduce something dramatic. They're just abbreviations for words, so you can use them in any way you'd use the words in essence or for example.

That's all.

1 versus   

prep.以…为对手，对；与…相比之下

参考例句：

• The big match tonight is England versus Spain.今晚的大赛是英格兰对西班牙。
• The most exciting game was Harvard versus Yale.最富紧张刺激的球赛是哈佛队对耶鲁队。

2 misusing   

v.使用…不当( misuse的现在分词 )；把…派作不正当的用途；虐待；滥用

参考例句：

• This means we must stop misusing them. 也就是说，我们已必须停止滥用抗菌素不可了。 来自英汉非文学 - 生命科学 - 预防生物武器
• Misusing organic fertilizer may cause a decrease in the soil's quality. 滥用有机肥料可能会导致土地的土质下降。 来自互联网

3 standing   

n.持续，地位；adj.永久的，不动的，直立的，不流动的

参考例句：

• After the earthquake only a few houses were left standing.地震过后只有几幢房屋还立着。
• They're standing out against any change in the law.他们坚决反对对法律做任何修改。

4 engrossed   

adj.全神贯注的

参考例句：

• The student is engrossed in his book.这名学生正在专心致志地看书。
• No one had ever been quite so engrossed in an evening paper.没人会对一份晚报如此全神贯注。

5 perfectly   

adv.完美地，无可非议地，彻底地

参考例句：

• The witnesses were each perfectly certain of what they said.证人们个个对自己所说的话十分肯定。
• Everything that we're doing is all perfectly above board.我们做的每件事情都是光明正大的。