These are abbreviations of Latin phrases. While they're often used interchangeably, they're actually two distinct phrases. That was one of the first rules that my sister Ruth taught me when I started editing!
E.g. stands for exempli gratia, or for the sake of example. I.e. stands for id est, or that is. I remember these by associating e.g. with example given and i.e. with in other words (to rephrase something you've said).
For example: My sister has taught me a lot about editing over the years, e.g., she explained the difference between e.g. and i.e. She has really been invaluable to me, i.e., she's been the editor's editor.
If you're tempted to use i.e. to introduce a list of items, remember that by definition it must include every possible example, while a list that opens with e.g. includes some, but not necessarily all, possible examples.
For example, in Section 22.1, Anatomy of a special report or white paper, I list ALL of the applicable levels that a problem may be impacting your reader, i.e., emotional, financial, mental, physical and spiritual.
Use a comma before and after either of these abbreviations, and try not to use them both in the same sentence.
The Chicago Manual of Style offers a bonus tip: if you start a list with e.g., there’s no need to put etc. at the end.
This post was an excerpt from The Customizable Style Guide for Coaches Who Write: Look Smarter, Write Faster and Get Better Results from Your Writing.