[Editor’s note: This post refers and links to the 17th edition of CMOS.]
Spotlight on “i.e.” and “e.g.”—and “etc.”
Latin may be a dead language, but many of its words and phrases flourish in modern English. The most common Latin borrowing might be an abbreviation: the all-purpose etc., short for et cetera, “and others of the same kind.”
The list of scholarly abbreviations at CMOS 10.42 includes about fifty Latin abbreviations, from ab init. (ab initio, “from the beginning”) to viz. (videlicet, “namely”). Many of these are found mainly in older sources but are listed for the benefit of historians and other researchers.
Others, like etc., remain in common use. These include i.e. (id est, “that is”) and e.g. (exempli gratia, “for example”), which are almost as common as etc. But because i.e. and e.g. can both introduce examples, people tend to mix them up. Another common mistake is to pair e.g. with etc.
Read on to find out more.
Specific vs. General*
In Chicago style, the abbreviations i.e. and e.g. are always spelled with periods, and they are always followed by a comma. In formal prose, their use is limited to parentheses, notes, and tables; outside of those contexts, they are usually spelled out (but in English). See CMOS 6.51 and 10.4.
The abbreviation i.e.—as its meaning of “that is” would imply—introduces a specific explanation or clarification of the text that immediately precedes it:
When the singular form of a noun ending in “s” is the same as the plural (i.e., the plural is uninflected), the possessives of both are formed by the addition of an apostrophe only.
When a quotation is introduced by an independent clause (i.e., a grammatically complete sentence), a colon should be used.
Sometimes the clarification will consist of one or more examples:
Before entering the room, we were asked to turn over any items that might be attracted to a magnet (i.e., jewelry, keys, and anything else with metal).
The abbreviation e.g., on the other hand, always introduces one or more examples (as its meaning, “for example” suggests). Unlike items introduced by i.e., these examples provide a general, open-ended illustration rather than a more specific clarification:
Titles of larger works (e.g., books, journals) are usually italicized, whereas titles of smaller works (e.g., chapters, articles) are presented in roman and enclosed in quotation marks.
In index entries, use an en dash rather than a hyphen in inclusive page numbers (e.g., “dogs, 135–42”).
Use etc. with i.e. (maybe) but not with e.g.
The best way to remember whether etc. should be used with i.e. or e.g. is not to use it at all. That’s because it should never be used with e.g., and it would only rarely be a good choice with i.e.
For example, you might be tempted to use etc. in the magnet example from the previous section:
Before entering the room, we were asked to turn over any items that might be attracted to a magnet (i.e., jewelry, keys, etc.).
But the original wording (“and anything else with metal”) is better because it’s more specific than etc. If you want to keep things general, use e.g. and limit what follows to examples (without tacking on an etc.):
Before entering the room, we were asked to turn over any items that might be attracted to a magnet (e.g., jewelry and keys).
not
Before entering the room, we were asked to turn over any items that might be attracted to a magnet (e.g., jewelry, keys, etc.).
It’s understandable that you’d want to add an etc. to what follows e.g., but resist the urge. The words for example imply the existence of other examples of the same kind—which is literally the meaning of etc. (as we learned at the beginning of this post). In other words, etc. is built into e.g., so adding etc. after the examples would be redundant.
* * *
To summarize, use i.e. for clarifications and e.g. for examples, avoid pairing etc. with e.g., and if you’re tempted to use etc. with i.e., it’s usually best to be more specific.
* Versus is another Latin borrowing, abbreviated v. in the names of court cases but often vs. in other contexts.
Top image by Karen Roach (modified for post) / Adobe Stock.
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Do you allow these abbreviations to be written without full stops? Etc, eg, ie.
Periods (full stops) are standard not only in Chicago style but also in the latest guides from the APA, MLA, and AP. But it’s common in science writing not to use periods (see, e.g., the AMA Manual of Style, 11th ed., 2020). And some styles omit the comma following “i.e.” and “e.g.”—whether periods are used or not. For example, New Hart’s Rules (2nd. ed., Oxford University Press, 2014) recommends periods in all three abbreviations but no comma following “i.e.” or “e.g.” And the online style guide for the British Guardian and Observer recommends “ie” and “eg” with no periods and no comma following (and also “etc” with no period). Whichever style you follow, be consistent.