Both i.e. and e.g. are abbreviations of Latin phrases used to clarify writing. They’re similar – but not identical – and getting them wrong can change the meaning of your document. Here’s a rundown.
An abbreviation for “id est,” i.e. is used to restate in different words what you’ve just said, i.e., to offer more information or be more explicit:
* A gratuity is already included in the bill, i.e., no tips are necessary.
* We offer new renters the standard discount, i.e., one month free.
* I like to play board games, i.e., Monopoly and Scrabble. (Note: using i.e. implies that those are the only board games you enjoy.)
An abbreviation for “exempli gratia,” e.g. is used to provide an example. Importantly, what follows e.g. is not a finite list but rather just a few examples from a longer list:
* Be sure to eat enough foods with protein, e.g., nuts, beans, and cheese.
* She was the star of many 6th grade activities (e.g., chess, soccer, and choir).
* I like to play board games, e.g., Monopoly and Scrabble. (Note: using e.g. implies you’re listing just a couple of the board games you like.)
Regarding mechanics, sometimes you’ll see these abbreviations in italics but that’s not required. What is required is a period after each letter, and the abbreviations are usually followed by a comma. Essentially, i.e. and e.g. are to be treated like the phrases they represent so use the same punctuation you otherwise would (e.g., you can use them in parenthesis, after a comma, a semicolon, or even a dash if you want emphasis).
Of course, whenever possible, it’s preferable to use English instead of Latin and full words (“in other words” or “for example”) instead of abbreviations. But i.e. and e.g. are certainly acceptable, especially when space is at a premium.
To our lawyer colleagues, please stop using i.e. when you mean e.g., because now you've just changed the meaning of the Order you asked the Judge to sign and we're going to have to come back to Court to clarify.