Yes, let’s complicate our lives further by adding a bit of Latin.
Etcetera means “the rest”–used at the end of the list to indicate that further, similar items are included. It can also be written as et cetera (two words) or as an abbreviated etc.
When written as an abbreviation, etc. should have a period. When etc. is in the middle of the sentence, always put a comma after it. Example: Please deliver to Emma the books, flowers, sheets, etc., that you will find in her bedroom.
When located at the end of the sentence, the period in etc. is also the terminal period of the sentence. Never put the word and before etc. because the et in et cetera already means and. The term in Latin means “and” (et) and “the rest” (cetera ).
The term et al. means “and other people”–used more appropriately for people too numerous to mention, as in a list of multiple authors. Do not use et al. for things. It is also an abbreviation so it has a period. If you mention only one person, it does not require a comma before it. Example: The conclusions of Reyes et al. are…” But if you have a list of persons, put a comma before the term, making the term part of the list. Example: Gonzalez, Villanueva, et al. No need to put a comma after et al.
Do we need to italicize or underline either term? No. Although they are Latin, these have become common terms already.
Disclaimer: Grammarians and stylists differ on how to style etc. and et al., as well as in many other areas of the English language. Oxford Journals, for instance, would not put a comma after etc. My suggestion? Choose the style (and logic) you prefer, then be consistent.
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