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It seems that "e.g." is always followed by a comma but "i.e." is not. Why is that?

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    It depends on whether American or British English is employed. See my answer below. Feb 28, 2015 at 18:24

9 Answers 9

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The distinction probably emerges from their different meanings in Latin, which grants them different usages in writing.

E.g. (exempli gratia in Latin, meaning “for example”) should be generally followed by a list of examples. Thus, adhering to proper English style usually requires commas to follow e.g. to delimit the beginning of that list.

I.e. (id est in Latin, meaning “that is”) is used to recapture the meaning of an antecedent clause by rephrasing. Typically, it is only followed by a clause describing a singular entity, and so does not require a comma.

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    @Tim I used neither term in their usual sense, I only referred to them as proper nouns. Besides, I did use a comma with the first e.g..
    – Uticensis
    Mar 13, 2011 at 12:41
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    I thought it was intentional. Please edit your answer so I can remove the upvote. :p
    – user4727
    Mar 13, 2011 at 12:43
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    Hm, you introduced an error in your second edit. You changed which means "that is" in Latin to which means "that is" is Latin...
    – Timwi
    May 3, 2012 at 12:39
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    It seems irrelevant that e.g. often has a list of items following it and i.e. does not; the introduction to the list has no need of being explicitly delimited from the e.g.
    – mgkrebbs
    Jan 25, 2014 at 6:31
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    I would put a comma after "That is"; by the logic of this answer, that would mean that "i.e." should be followed by a comma too. Sep 23, 2014 at 17:53
119

Grammar Girl did some research and determined that five out of six style guides lean toward using a comma after both i.e. and e.g. Here's the gist of the table she shared on her site:

  • Chicago Manual of Style: A comma is usually used
  • Blue Book of Grammar and Punctuation: Commas are preferable/optional
  • The Columbia Guide to Standard American English: Editors require a comma
  • The Guide to Grammar and Writing: The commas make good sense
  • Lynch Guide to Grammar: Should be followed by a comma
  • Fowler's Modern English Usage: Commas do not usually follow i.e. (No comment on e.g.)

She also gives an excellent rundown on when to use each of these abbreviations. She suggests that you think of i.e. as meaning "in other words" and e.g. as meaning "for example." I recommend reading her entire article.

Addition: My daughter just reminded me of an excellent and entertaining explanation of usage for i.e. and e.g. from The Oatmeal. This one I can't summarize. You must view it in all its glory.

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    Good link, Kristina, probably better than my answer. It'd help if you'd summarize the most useful part of your link for the benefit of readers so they might not have to click through. It's easy rep points, and besides, links are susceptible to link rot, i.e. they die.
    – Uticensis
    Mar 13, 2011 at 18:40
  • thanks for the great link, +1. I agree with @Billare that if possible please summarize the key takeaways from that article. It will be helpful to readers on this site.
    – evergreen
    Mar 13, 2011 at 22:35
  • @Billare & @evergreen, Thanks for the suggestions. Will edit. : )
    – Kristina
    Mar 14, 2011 at 20:28
  • I like how the Oatmeal cartoon specifically addresses the comma issue, stating that most style guides recommend using a comma after the abbreviation, and yet in this panel, they have one ‘i.e.’ with a following comma, and one without! Aug 26, 2013 at 8:43
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    For British English: the Oxford, Guardian and Telegraph style guides all avoid using a comma after 'eg'. Grammar Girl, the source for this answer, also mentions this difference with British English.
    – James EJ
    Aug 7, 2017 at 18:07
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I was drawn to this question by edits that I made on other SE sites, constantly being re-edited and commas being added after an "e.g." that I had added, without the comma. After the umpeenth time, I decided to check whether I was wrong, and had been making the same mistake for 40 odd years. I was quite sure that the use of a comma was incorrect and had not really seen it used before.

I liked @Kristina's answer, but still ever doubtful, I decided to follow the links provided in the answer. It turns out to be a linguistic cultural difference between American English and British English. In American English the additional comma appears to be quite prevalent, whereas in British English it is very rarely seen/used.

From Grammar Girl - I.e. Versus E.g. (Page 2)

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.

So, in short, I am happy to say that, as a Brit, I am not wrong in my refusal to add the comma, but then again, neither are the subsequent editors of the text. It just depends upon which flavour of English one uses natively. ;-)

However, ironically, after "for example" I add a comma.

In addition, for completeness, I would not use a comma after "i.e.", although I would after "that is to say".

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  • I suffer this constantly, i.e. someone adding commas to my e.g. and i.e., when working on shared documents. It can be so frustrating.
    – Daniel
    Jul 6, 2021 at 15:58
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It is not true that i.e. is never followed by a comma, nor that e.g. is always followed by a comma. You could also write sentences like the following.

Similar dynamics that resulted in the development of new local art forms have been documented elsewhere (e.g. Chibnik 2008).

My walking boots are synthetic, i.e., not leather or suede.

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    +1 for deciding individually for each case. I really dislike the widely-used rule that “e.g.” (and sometimes “i.e.”) is always followed by comma. Mar 13, 2011 at 16:00
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I am late to the party, but among all the excellent citations given in support of using or not using a comma after i.e. and e.g., let me also mention what New Hart's Rules (2005) from Oxford University mentions in the chapter Punctuation>Comma>Other uses (4.3.8):

Depending on the structure of the sentence as a whole, a comma may or may not be used after namely and for example:

The theoretical owners of the firm, namely the shareholders ...

We categorized them into three groups—namely, urban, rural, or mixed

A comma is generally required after that is. To avoid double punctuation, do not use a comma after i.e. and e.g.

I am going to go with Oxford’s recommendation of not using a comma after either i.e. or e.g. purely for aesthetic reasons.

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According to Fowler's "Modern English Usage", as quoted in Daily Writing Tips, “whether a comma follows [e.g.] or not is indifferent, or rather is decided by the punctuation-pitch of the writer of the passage.” He says nothing of “i.e.”, but I go by the same idea.

A comma signals a slight pause. If I speak what I write, would I pause there?

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I think it’s clear that e.g. has to have full stops/periods. As for using a comma after it, that should only be done in some rare cases, as in the sentence “e.g., i.e., and other abbreviations of Latin forms are often a source of confusion for English learners.” In other cases, I can see no logical reason for it to be used except a puzzling convention followed by some writers. As for convention, style guides typically don’t recommend this. Why not follow logic rather than convention, or if you follow convention, follow all major style guides, which use e.g.? I recently wrote a blog post on this issue at http://www.makeyourenglishwork.com/2012/05/17/eg-or-e-g/ if you’re interested.

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    I strongly agree that one should write “for example” and “that is” — or their equivalents — out in full and in English.
    – tchrist
    May 17, 2012 at 19:03
  • "I can see no logical reason for it" I can see a logical reason: I.e. and e.g. are typically stand-ins for parenthetical phrases, and parenthetical phrases are often set off from the rest of a sentence by commas. I don't think there's anything puzzling about that. Also note that the comma is recommended by at least two of the style guides you reference the blog post you linked. Dec 15, 2017 at 0:24
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I think we will usually use a comma. We can confirm the same by substituting the abbreviation with original word, i.e., with "For example" and "That is" in this case. E.g.:

I like you, that is, I think I like you.

Although I am not sure what will be case if the sentence ends with e.g. or i.e.

  • I think I will die soon. I did not do anything in my life. But still it might not be a complete waste, i.e. (e.g.)...
  • I think I will die soon. I did not do anything in my life. But still it might not be a complete waste, i.e. (e.g.),..

The first one seems correct to me.

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I would always place a comma after ie. and eg.

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    You lack a couple of periods... :-) I've not down voted you though. Feb 28, 2015 at 17:59
  • English Wiktionary gives "ie" and "eg" as acceptable variants of "i.e." and "e.g." but I have never seen this used in practice. Apr 25, 2020 at 18:16
  • The Economist style guide (12th ed.) uses "ie" and "eg", i.e., without punctuation.
    – Erik
    Aug 27, 2020 at 8:03
  • @Nicole Sharp This has been discussed before too. I use this practice (it prevents terrible clutter where other punctuation must immediately follow). But these are style recommendations, not fiats. I've come across one respected style pundit who says decent writing doesn't use such abbreviations at all. May 13, 2021 at 10:36

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