Latin, though dead through and through, has undoubtedly pushed its way into the English language in an important way. Not enough of us these days know how to wrangle it properly, though. “Quid est?”, or “What is that?”, will help you with Latin lingo and lore.
So what are i.e. and e.g.? We start talking about words, i.e. groups of letters, e.g. groups, of, letters, and suddenly these two abbreviations beg to show up. Which one should you use, though?
i.e. stands for id est, Latin for “that is”. Use it to clarify what you’re saying. For example, I might be talking about an hour, i.e. sixty minutes.
e.g. stands for exempli gratia, Latin for “for the sake of example”. Use it to give a couple examples for what you’re saying. For example, I might be talking about different time zones, e.g. Eastern Standard Time, Greenwich Mean Time, or Western Indonesian Time.
In conclusion, think of i.e. as “that is”, and e.g. as “for example”. Now you don’t have to mix them up the next time you use them!