Latin abbreviations are quite common in standard English, but they are also commonly misused. Here are some popular examples, what they mean, and how to use them correctly.
Of course, etc. stands for et cetera, meaning "and the rest" or "and others." Use etc. to indicate a continuing list of things that don't need to be specified. When using etc., do not begin your list with a phrase like "such as," which already indicates that your list will be incomplete.
"I packed sandals, towels, sand toys, etc., into the trunk."
"I packed the trunk with sandals, towels, sand toys, etc."
As shown above, use a comma before and after etc. when it falls mid-sentence. When using etc. at the end of a sentence, the period that ends etc. will also end the sentence, unless you want the end punctuation to be something other than a period:
"Did you bring sandals, towels, sand toys, etc.?"
Friendly note: The phrase is ET cetera. "ECK cetera" is incorrect and, frankly, a little embarrassing.
2. e.g. and i.e.
When you've named a broad category of things and wish to give an example or two, you may use e.g., which means exempli gratia, or "for example."
When you've used a word or phrase that the reader may not fully appreciate without clarification, use i.e. (id est) to mean "that is to say" or "in other words." Often, i.e. is used to impart an extra layer of meaning.
"Karen hopes to enter a caring profession, e.g., nursing or psychology."
"Julia wants to be in real estate or finance, i.e., a profession with high earning potential."
3. a.m. and p.m.
We know these abbreviations indicate whether a time is before (ante) or after (post) the noon hour (meridian), but should they be capitalized, and should we use periods?
As with i.e. and e.g., the standard in American grammar is to use lowercase letters with periods after each. However, the standard in English grammar outside the U.S. is to omit the periods. When writing for an institution or business, find out if they have a preferred style. Consistency in usage is, in these cases, more important than personal conviction.
Confusion over whether "12 a.m." or "12 p.m." is correct is simply handled; use the words "noon" and "midnight" instead. This principle applies to the other abbreviations as well; when in doubt, feel free to use the English phrases they represent. In fact, when your writing task calls for formal language, the use of abbreviations may be discouraged.
The best way to internalize language rules is to consider many examples and explanations. Browse various grammar sites and visit this space often for useful usage tips, interesting insights, and learned language!