A Sick Look at "i.e." and "e.g."

Two closely related items that are often interposed are i.e. and e.g., both Latin abbreviations, and as such potentially off-putting to some readers, which can result in people never nailing down the distinction. At their most basic level, i.e. means in other words and e.g. means for example. (Please note that i.e. and e.g. are not italicized in common usage. I italicize them here because they are being referred to and not used per se).

The way my mind got straightened out on i.e. was a string of synonyms delivered by a teacher expressing exasperation over our class’s slow pace in grokking the matter: “In other words, that is to say, so to speak, if you will, I.E.!!!”

The Latin phrase it abbreviates is id est, translating directly as that is, but in keeping with usage, it is best thought of as in other words. Its function is to set up an alternate description, usually one in finer detail: “I have flu symptoms, i.e., fever, sore throat, cough, chills and fatigue.” As a side note, correct punctuation of i.e. is to include a comma after the second period.

One could also write, “I have flu symptoms, e.g., fever, sore throat, cough, chills and fatigue.”  There would be a different inference taken with e.g., however. The letters e.g. are an abbreviation of exempli gratia, which can be translated as for example.

The abbreviation i.e. carries with it a sense of finality in that what follows i.e. is a practical equivalent of what precedes it, expressed in other words. In our example then, the fever, sore throat, cough, chills and fatigue constitute all of the symptoms being experienced.  

With e.g., you are merely citing examples, and you could very well be supplying only a partial list. In the case of the flu symptoms illustration, if my last bout with the flu is any barometer, the writer has probably left off runny nose, nausea and vomiting for the sake of decorum.