For abbreviations that are so commonly used, i.e. and e.g. cause massive problems for both readers and writers.
I.e. stands for id est, which is Latin for “that is.” You use it wherever you would use the words “that is” in a sentence. In the following examples, you could replace “i.e.” with “that is” and the sentences would still be correct.
I am the big cheese, i.e., the boss.
I am eating the fruit I like the best, i.e., the avocado.
E.g. stands for exempli gratia, which is Latin for “for the sake of an example.” You use it wherever you would use the words “for example” in a sentence. Just as for i.e., you could replace “e.g.” with “for example” in the following sentences and they would still be correct.
I think small dog breeds, e.g., the Chihuahua, are cute and I can’t wait to get one.
Important Japanese buildings, e.g., Tokyo Tower, usually get blown up in post-apocalyptic animes.
Brian Klem from The Writer's Digest suggests a couple of clever mnemonics to help you use this troublesome duo correctly.
To burn these definitions into your memory and help remind you which letter-abbreviation pairs with which definition, you can follow this mnemonic device a college friend once taught me: i.e. is "in essence" while e.g. is "eggs sample."
Correctly Punctuating i.e. and e.g.
The periods that are part of i.e. and e.g. tend to mess people up when it comes to punctuation. The easiest way to remember how to correctly punctuate these abbreviations is to pretend they are the words “that is” and “for example” and then punctuate them accordingly.
Take these sentences, for example:
Sam drinks hard liquor, e.g., whiskey, and therefore has a high alcohol tolerance.
Sam drinks hard liquor, for example, whiskey, and therefore has a high alcohol tolerance.
My favorite opera will always be the one I was named after, i.e., Bizet’s Carmen.
My favorite opera will always be the one I was named after, that is, Bizet’s Carmen.
Notice that i.e. and e.g. are always preceded and followed by a comma when in use. The only exception to that is when they start a sentence, in which case they’re only followed by a comma.
Here’s a cute video about using i.e. and e.g. correctly, just in case you need more elucidation on the topic.
Punctuation: How To Use i.e. And e.g.