Should I always use a comma after “e.g.” or “i.e.”?

Question

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

Answer 1

The distinction probably emerges from their different meanings in Latin, which grants them different usages in writing. E.g., or exempli gratia in Latin, "for example", should be generally followed by a list of examples; thus adhering to proper English style usually requires commas to follow e.g. in order to delimit the beginning of that list. I.e., short for id est, which means "that is" is Latin, is instead used to recapture the meaning of an antecedent clause by a rephrasing, so it is generally only followed by a clause describing a singular entity, and thus need not require a comma.

Answer 2

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 (link below).

• 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 makes good sense
• Lynch Guide to Grammar: Should be followed by 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 whole article: http://grammar.quickanddirtytips.com/ie-eg-oh-my.aspx.

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

Answer 3

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.

Answer 4

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.

Answer 5

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.

Answer 6

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