This week I'm covering a request. That's right, a request. [embed]https://twitter.com/DPernitsky/status/560112062618025985[/embed]
Hooray! It's nice to know someone else obsesses over this stuff. Thanks for the idea, Dustin.
So when should I use an s' or an s's?
As much as I hate to say this, there is no correct answer. Everyone disagrees (especially among academics) and there isn't a hard and fast rule.
Even the book I use as a punctuation style guide—Eats, Shoots & Leaves, by Lynn Truss—doesn't have a straight answer for it:
Current guides to punctuation (including that ultimate authority, Fowler's Modern English Usage) state that with modern names ending in "s" (including biblical names, and any foreign name with an unpronounced final "s") the "s" is required after the apostrophe:
Philippa Jones's book
St James's Square
Alexandar Dumas's The Three Musketeers
With names from the ancient world, it is not:
If the name ends in an "iz" sound, an exception is made:
And an exception is always made for Jesus:
However, these are matters of style and preference that are definitely not set in stone, and it's a good idea not to get fixated on them.
Wait, what? The subhead of this book is "The Zero Tolerance Approach To Punctuation," and she still doesn't have a straight answer? Seriously, why does anyone speak this language?
The short answer: you can't go wrong.
If you're writing for someone else, ask them. If you're using a style guide, follow that. My personal preference is the character-saving (and, in my opinion, easier to read) s', but make your own decision. It shouldn't really matter as long as people understand you.
Just pick one and stick with it.
And if anyone ever criticizes you for "improper usage?" Feel free to send them my way.