That Is, For Example, and the Rest
Latin is referred to as a dead language, yet many of us use it frequently—though, perhaps, unknowingly.
Think of how often you see i.e., e.g., and etc. All three are abbreviations of Latin phrases. While certainly not dead, however, one might say they are often ill (ill-used, that is).
That Is
Let's start with i.e. It stands for id est, meaning that is. This abbreviation is interchangeable with in other words, and it is properly used to introduce a definition or clarification of the preceding word or phrase.
Her business's focus is technical writing, i.e., translating difficult subject matter into clear, concise content.
Standard English abbreviations are easily pronounced when read aloud (if you see Mr., you'll automatically say "Mister"). But it's safe to say most people wouldn't know id est. If you find yourself having to recite copy with i.e., you can just pronounce each letter. However, to avoid confusion, say "that is" instead.
While not necessarily incorrect, it is better to avoid using i.e. to introduce a list of examples. (That's what e.g. is for.)
For Example
E.g. stands for exempli gratia, which translates into for example. It's used to introduce a short list to help identify what is being discussed.
She writes about a wide variety of topics, e.g., medical devices, software, and financial planning.
E.g. is also read aloud by pronouncing the letters, but "for example" is a good substitution.
Because e.g. specifically calls for examples, it is incorrect to have it precede a clarifying description. (That's what i.e. is for.)
And the Rest
Do I need to state that etc. stands for et cetera? Who hasn't used this Latin phrase (even if unsure of how to spell it out)? It translates as and the rest, and concludes items in a series.
Her business website includes contact information, writing samples, testimonials, etc.
There are three common mistakes made with etc. The first is preceding it with the word and. Because et means and, it is redundant to write and etc.
The second mistake is to use etc. at the end of a list that is preceded by e.g. or for example. Keep in mind that for example—whether expressed in Latin or in English—implies that the subsequent list is a partial one, i.e., it is assumed that other examples exist. Therefore, it is redundant to end such a list with etc.
The third common error is adding an extra period when etc. is at the end of a sentence. In such cases, one period does double duty, ending both the abbreviation and the sentence.
By the way, while fans of The King & I may love to say "et cetera, et cetera, et cetera," only one etc. is generally used when writing.
Making Comma Sense of It All
Note in the examples above that i.e. and e.g. are followed by commas. A comma (or a colon) is required after each. They are also preceded by some punctuation, such as a comma, a dash, or an opening parenthesis.
She understands how to write performance-support materials (e.g., standard operating procedures and job aids).
Because it ends items in a series, etc. should be preceded by a comma. Equivalent phrases (such as "and so forth" and "and the like") are followed by a comma when a sentence continues, and it is acceptable to use one after etc. (first example below). However, if not otherwise needed to separate clauses, this second comma can be dropped, since etc. is generally treated like the last item in the series (second example below).
Her collection includes a number of style manuals, grammar guides, reference books, etc., so the shelf above her desk is quite full.
Style manuals, grammar guides, reference books, etc. fill the shelf above her desk.