When you are writing something (e.g. an article, book, blog) and you want to add some more information (i.e. supplement your text with additional facts) then it’s time to pull out your letters. (i.e. e.g. and i.e.) (e.g. i.e., e.g.)
The trouble is knowing which one to use. Having just learned this myself, I shudder to think of my willy-nilly usage that is no doubt scattered throughout this blog. Each has its specific purpose and meaning.
i.e. is an abbreviation of the Latin phrase id est. You can think of it as meaning “that is to say”, and it can be used to re-phrase or elaborate upon your thought in order to increase understanding. (i.e. another way of saying it might make more sense to the reader)
e.g. is quite different and is an abbreviation of exempli gratia that can be taken to mean “for example”. So you could complete your thought then include a brief list of supporting cases. As a side-by-side comparison…
I like felines. (e.g. cougars, cheetahs, pumas)
I like felines. (i.e. the Felinae subfamily of the Felidae family)
In order to remember the difference it may be helpful to think of e.g. meaning “examples given”. (or maybe just “eg-zample”?) It is suggested that i.e. could equal “in effect” but that seems obtuse to me. I’ll remember “examples given” and i.e. simply becomes “the other one”.
Bonus points if you don’t add etc. to the end of your list of examples. The etcetera is redundant as e.g. already defines it as an incomplete list.
- Source: Common Errors in English Usage