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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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10 Answers 10

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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
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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 but 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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  • 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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Following up on Kristina's answer from 2011, I have gathered content from various style guides that bears on the question of whether or not to add a comma after i.e. or e.g. Because the split between U.S. usage and British usage on this point is so wide (and seems to have widened further in recent decades) I have separated the excerpts into three categories, based on their country of origin, and then arranged them chronologically within each.



British English style

From Henry Fowler, A Dictionary of Modern English Usage (1926):

e. g. is short for exempli gratiâ, & means only 'for instance'. Non-latinists are apt to think that it does not matter whether e. g. or i. e. is used ; so Mr —— took as the theme of his address the existence of what he called a psychic attribute, e.g., a kind of memory, in plants. Italics, & a following comma, are unnecessary, but not wrong.

...

i. e., id est. ... 4. It is naturally preceded by a stop ; whether a comma follows it or not is indifferent, or rather is decided by the punctuation-pitch of the writer of the passage.

From Henry Fowler & Ernest Gowers, A Dictionary of Modern English Usage, second edition (1965):

e.g. is short for exempli gratiâ, and means only 'for instance'. ... Italics, and a following comma, are unnecessary, but not wrong. Both abbreviations [e.g. and i.e.] should be reserved for footnotes or very concise writing; in open prose it is better to write for example or for instance; namely or that is to say.

...

i.e., id est. ... 4. It is naturally preceded by a stop; it should not be followed by a comma unless the sense requires one, to introduce a parenthesis for instance. He attacked reactionaries, i.e. those whose opinions differed from his own, but He attached reactionaries, i.e., it would seem, those whose opinions etc.

From Michael Swann, Practical English Usage, second edition (1995):

13 [discourse markers] giving examples ... In writing, the abbreviation e.g. (Latin exempli gratia)... is often used to mean 'for example'. [Example:] Some common minerals, e.g. silica or olivine, ...

Although Swann doesn't directly address the question of whether to follow "e.g." with a comma, the only example he provides lacks such a comma.

From The Oxford Guide to Style (2002):

3.8 e.g., i.e., etc. Do not confuse 'e.g.' (exempli gratia), meaning 'for example', with 'i.e.' (id est), meaning 'that is'. Compare hand tools, e.g. hammer and screwdriver with hand tools, i.e. those able to be held in the user's hands. Print both in lower-case roman, with two points and no spaces, and preceded by a comma. In OUP style, 'e.g.' and 'i.e.' are not followed by commas, to avoid double punctuation; commas are often use in US practice.


Canadian English style

From Margery Fee & Janice McAlpine, Guide to Canadian English Usage, second edition (2007):

i.e., e.g. An abbreviation of the Latin phrase id est, i.e. means 'that is'; e.g. is an abbreviation of exempli gratia, meaning 'for example'. The meanings of these two abbreviations are different: i.e. introduces a paraphrase or further explanation, while e.g. introduces an example. Both of these abbreviations require two periods because thy abbreviate two words.

Although Fowler's (1965) suggested that these abbreviations should appear only in notes, and the Chicago Manual of Style confines them to notes and parenthetical comments, they appear increasingly in running text in works of all kinds. Most guides recommend that i.e. and e.g. be preceded and followed by commas. They need not be italicized.


U.S. English style

From Bergen Evans & Cornelia Evans, A Dictionary of Contemporary American Usage (1957):

i.e., and e.g. have distinctly separate meanings. i.e., which is an abbreviation of the Latin id est (that is),introduces a definition (He threatened them with massive retaliation, i.e. the hydrogen bomb). e.g., which is an abbreviation of the Latin exemplia gratia (for example), introduces an illustration (He avoids all frivolous diversions, e.g. dancing).

Although this entry doesn't directly address the issue of whether to include a comma after e.g. or i.e., it presents examples of each that omit the comma. This makes Evans & Evans unique among the U.S. style and usage guides that I consulted.

From Words into Type, third edition (1974):

For example, that is, and similar phrases introducing an illustration or an explanation should usually be set off [with a comma] from the rest of the sentence. The comma is sometimes omitted after thus, hence, namely, and the abbreviations e.g. and i.e. For instance or for example used after the illustrative phrase may need no comma before it. Clearness may require setting off the illustration or explanation, together with the introducing phrase, by dashes or parentheses.

From [Merriam-]Webster's Dictionary of English Usage (1989):

i.e., e.g. ... I.e., like that is, typically introduces a rewording or clarification of a statement that has just been made or of a word that has just been used:

Most of the new books are sold through 3,500 Christian (i.e., Protestant) bookstores —N.Y. Times Book Rev., 31 Oct. 1976

It is money that wasn't absorbed by the government, i.e. the administration tax cuts, that is spurring current growth —Joe Sneed & John Tatlock, Houston Post, 31 Aug. 1984

E.g. introduces one or more examples that illustrate something stated directly or shortly before before it:

Poets whose lack of these isn't made up by an inescapable intensity of personal presence (e.g. Sylvia Plath) simply aren't represented —Hugh Kenner, N.Y. Times Book Rev., 17 Oct. 1976

... rent them to responsible tenants, e.g., retired naval officers —David Schoenbaum, N.Y. Times, 3 July 1977.

Like Evans & Evans, WDEU doesn't discuss whether e.g. and i.e. should be followed by a comma, but in sharp contrast to Evans & Evans, WDEU splits its four real-world examples into two that include commas and two that do not.

From Kenneth Wilson, The Columbia Guide to Standard American English (1993):

e.g., i.e. (abbrevs.) Properly used, each of these ids Standard. I.e. abbreviates Latin id est, "that is"; use it when you wish to repeat in different words what you've just finished saying: I'm strongly opposed; i.e., I'm determined no to cooperate. E.g. abbreviates the Latin exempli gratia, "for the sake of example, for example." People sometimes say the names of the letters i and e or e and g instead of saying the English that is or for example, but the abbreviations aren't much shorter, and most of us would prefer the English words in speech, no matter how familiar the Latin abbreviations are in writing. Note carefully the punctuation and typeface (roman or italic) requirements of use; these may vary with the publisher. Most editors put them in italics; all require a comma after the second period.

From Patricia O'Conner, Woe Is I: The Grammarphobe's Guide to Better English in Plain English (1996):

e.g./i.e. Go ahead. Be pretentious in your writing and toss in an occasional e.g. or i.e. ... Both e.g. and i.e. must have commas before and after (unless, of course, they're preceded by a dash or a parenthesis).

From Joseph Gibaldi, MLA Style Manual, second edition (1998):

e.g. for example (from Lat. exempli gratia; rarely capitalized; set off by commas, unless preceded by a different punctuation mark)

...

i.e. that is (from Lat. id est; rarely capitalized; set off by commas, unless preceded by a different punctuation mark)

From Mark Davidson, Right, Wrong, and Risky: A Dictionary of Today's American English Usage (2006):

e.g. or i.e.? A common error in conversation and casual writing is to use i.e. in place of e.g. ... Note that e.g. and i.e., like the English phrases they substitute for, should be followed by a comma or a colon. Usage examples: "Shortages of qualified applicants seem to be chronic in certain occupations, e.g., nursing and schoolteaching." "The majority ethnic group in Sri Lanka (i.e., the Sinhalese) were involved in a long conflict with the minority Tamils."

From Bryan Garner, The Redbook: A Manual of Legal Style, second edition (2006):

eg.; i.e. The first is the abbreviation (for exempli gratia) that you want when citing examples <top-tier law schools, e.g., Yale, Harvard, and Michigan>. The second (short for id est, "that is") is used where further explanation is due <the Framers insulated Article III judges from the political fray, i.e., they are appointed for life and not easily subject to removal>. But i.e. is often misused to mean "for example." Despite their appearance to the contrary in this entry, e.g. and i.e. should not ordinarily be italicized, and they should each be followed by a comma. One exception is e.g. in legal-citation signals such as see., e.g., which are italicized.>

From The Associated Press Stylebook (2007):

e.g. Meaning for example, it is always followed by a comma.

...

i.e. Abbreviation for the Latin id est or that is and is always followed by a comma.

From Bryan Garner, Garner's Modern American Usage, third edition (2009):

e.g. A. Generally. This abbreviation, short for exempli gratia {L. "for example"}, introduces representative examples. In AmE, it is preferably followed by a comma (or, depending on the construction, a colon) and unitalicized. In BrE, curiously enough, the periods are sometimes omitted—e.g.: "The problem with seeking a legislative cure for the ethical disease is that most of the perceived outrages are either already illegal (eg, Pentagon officials taking bribes) or beyond the reach of the law (politicians' sexual adventures)." "Washington on an Ethics Kick," Economist, 28 Jan.—3 Feb. 1989, at 19. To American eyes, eg looks like egg misspelled.

...

i.e. ... D. Punctuation. Generally, a comma follows i.e. in AmE (though not in BrE). E.g.:

  • "The implicit assumption is that the fountains were designed for some wading—i.e., 'interactive participation." "Tempest in a Memorial Pool," Wash. Post, 3 Aug. 1997, at C8.
  • There was absolutely no need for any U.S. network to 'cover' (i.e., 'interpret') the funeral." Letter of Mary L. Spencer, "Too Much Talk," Indianapolis Star, 2 Oct. 1997, at E7.

From The Bluebook: A Uniform System of [Legal] Citation, nineteenth edition (2010):

E.g., Cited authority states the proposition; other authorities also state the proposition, but citation to them would not be helpful or is not necessary. "**E.g.," may be used alone or attached to any other signal (whether supportive or not). When it is attached to another signal, it should be preceded by an italicized comma and followed by a non-italicized comma. [Examples:] See, e.g., | But see, e.g.,

From The Chicago Manual of Style, sixteenth edition (2010):

6.43 Commas with "that is," "namely," "for example," and similar expressions. Expressions of the type that is are traditionally followed by a comma. They may be preceded by an em dash or a semicolon, or the entire phrase they introduce may be enclosed in parentheses or em dashes.

...

The abbreviations i.e. ("that is") and e.g. ("for example"), if used in formal writing, should be confined to parentheses or notes and followed by a comma.


Assessment

British style guides have moved away from the ambivalence about including or omitting a comma after e.g. or i.e. expressed by Fowler in 1926—first to Gowers's tolerance of the comma after e.g. but hostility toward the comma after i.e., and eventually to Oxford's blanket rejection of the comma in either case "to avoid double punctuation."

In contrast, U.S. style guides have become much more pro-comma since 1974, when Words into Type rather blandly noted that "the comma is sometimes omitted." Of the nine U.S. style guides published after 1989 that I checked, eight are very nearly as categorical in requiring the comma as Oxford is in rejecting it.

The Canadian guide merely reports (accurately) the predominant preference in North American style guides for including the comma.

Because punctuation is ultimately a matter of stylistic preference rather than grammatical necessity, writers who are not obliged by their publisher to follow a particular style guide are free to adopt the style that they like better—even if that means defying the prevailing style in their country—just as a U.S. writer can choose to use the spelling colour and, conversely, a British writer can choose to use the spelling color.

Nevertheless, UK and U.S. style preferences on this point have clearly diverged in recent decades, with prominent style guides on both sides of the Atlantic taking a less laissez-faire attitude toward the matter.

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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
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    "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
  • The use of full stops with eg and ie is certainly not mandatory, as a quick check online will show. Cambridge Dictionary and Collins, for instance, list both variants. The dropping of full stops seems more prevalent in the UK than in the US; it certainly avoids a lot of clutter (eg i.e.,). Rarely does it cause a lack of clarity. Jul 13, 2023 at 11:11
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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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