Quirks of English

--for those who speak English as their second language or who just want to improve their writing

(Text-only version of Quirks of English)

e.g. or i.e.?

Although they look similar, the often confused abbreviations e.g. and i.e. have different meanings and should not be used interchangeably. Consider that e.g. is not an abbreviation of the Latin ergo, which means therefore, but of the Latin exempli gratia, which means for example. In contrast, i.e. is an abbreviation of the Latin phrase id est or that is.

Except in parentheses, NASA Lewis style is to use that is and for example instead of these abbreviations. In parentheses, the proper choice depends on your intended meaning. Use e.g. if what follows is an example, or a partial listing, of what comes before e.g.:

This is true of all near-Earth asteroids (e.g., Orpheus and BX3).

This is a sampling of such asteroids, not an exhaustive list.

Use i.e. if what follows is another way of saying or explaining what comes before i.e.:

Surface-tension-driven convection is masked by gravitational effects in normal gravity tests (i.e., tests at 1g).

Here, "tests at 1g" is another way of saying "normal gravity tests."

Also use i.e. if a complete list is given:

Several desktop computing platforms are in use at Lewis Research Center (i.e., IBM-compatible, Macintosh, and UNIX platforms).

Test yourself.

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Last updated: 1/20/2009