Yesterday, I stumbled upon an old post from Grammar Girl:
E.g. means “for example,” so you use it to introduce an example: I like card games, e.g., bridge and crazy eights. Because I used e.g., you know that I have provided a list of examples of card games that I like. It’s not a finite list of all card games I like; it’s just a few examples.
On the other hand, i.e. means “in other words,” so you use it to introduce a further clarification: I like to play cards, i.e., bridge and crazy eights. Because I used i.e., which introduces a clarification, you know that these are the only card games that I enjoy.
I have a bachelor’s degree in English education, but through four years of college time, I had never heard of this being spoken of by any lecturer nor had I felt the urge to ask about it. I forgive you if you’re worried about my students, knowing that I’m a certified teacher; but don’t fret, I am an editor for a magazine—not educational one, by the way—and currently not teaching anyone.
One thing I find funny about the difference between i.e. and e.g. is that I had always thought of it as just a matter of consistency—consistency as in deciding whether to use British English or American English. During the time I attended four writing courses, there was one principle idea that I always kept in mind; i.e., never use British English and American English simultaneously.
A good example of common mistakes in this context is, “I never realised that I was a member of a college organization.” Note the word “realised” and “organization” here—this (spelling) is the most common and noticeable difference of British English and American English, with the latter word being the American one. However, this kind of mistake is also sometimes considered mistyping—the letter “Z” is located below the letter “S” if you use QWERTY layout.
Thank God I came across this Grammar Girl’s post. Personally, I don’t use “i.e.” and “e.g.” that often, but in some cases, they are essential—as you can see in the previous paragraph, where the former clarifies “the principle idea” I was talking about. If you’re not into reading hundreds of words, though, the Oatmeal has a nice comic strip of the exact same topic.