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If I remember correctly from English class, then one should put a comma after "i.e.", i.e., the Latin abbreviation for id est.

But lately I've seen the comma after "i.e." dropped in books. So what is the rule or consensus here if any?

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Think of it this way: pretend you're using "in other words" instead of "i.e.". How will you punctuate your sentence? –  user730 Dec 16 '10 at 11:06
I would always put a comma after i.e. Do you have examples where you wouldn't? –  Michael Dec 16 '10 at 11:09
So, put a comma after "i.e.". :) The two are supposed to be interchangeable; if it looks funny when you replace one with the other, then probably the sentence construction is dodgy. A similar test exists for distinguishing "its" and "it's". –  user730 Dec 16 '10 at 11:12

5 Answers 5

up vote 23 down vote accepted

Some books & journals use American English, while some use British English. In the American style of writing, a comma is inserted before and after i.e. However, in the British style of writing, a comma is inserted before but not after i.e.

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It seems that the use of comma is found more often in American English, and even there, it is not always required.

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.

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Personally, my UK-centric view is that I would put a comma after 'that is'; that is, if I were to use the long-hand, so to speak.

But I would not put a comma after 'id est'; i.e. although it may seem 'correct', I feel it impedes understanding, rather than aiding it.

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As indicated in The Elements of Style, abbreviations are "parenthetic and should be punctuated accordingly". It also says "never omit one comma and leave the other". For me, this means if you put a comma before "i.e.", there has to be another comma after it.

I don't think every rule in The Elements of Style is critical or mandatory to proper writing, but it is safe and trouble-free to follow most of them.

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'The Elements of Style'? Pfff! See here:chronicle.com/article/50-Years-of-Stupid-Grammar/25497 –  Barrie England Nov 15 '11 at 20:16
lol. I knew this would happen so added the 2nd paragraph there. :) –  Yang Chi Nov 15 '11 at 20:28
It is not safe, nor trouble-free, to follow the rules. They are idiotic and describe nothing. Pay no attention to them. –  John Lawler Aug 26 '13 at 16:35

I have been doing technical writing for over 30 years and have always separated the substitution with a comma. For some years, printers dropped the comma to save ink and space. I refuse to accept cost as a reason to override logic and clarity.

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protected by tchrist Jul 1 at 0:47


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