Everyone knows the rule (not universally followed) that when a word ends with the letter S, we just add an apostrophe right after the word, instead of adding an apostrophe and an S after it. So, according to the above rule of thumb, it's

Mary's book

Johns' wife

Mike's pencil

Copernicus' theory

The noun itself is pronounced fully with an S at the end, and then the S sound is pronounced immediately.

But there's another category of words that end with an S - i.e. most plurals. In this case, at least in writing, we (again, not universally) follow the same rule:

April Fools' Day

Mathematicians' paradise

Parents' house

But I have noted that in the second case, the missing S after the apostrophe is not pronounced at all, even in formal speech.

Is this normal?

  • 1
    Are you asking about (e.g.) /*parents*/ vs /*parentses*/ in the pronunciation? – Lawrence Jul 21 '16 at 14:15
  • @Lawrence that's exactly what I'm doing. – Michael Smith Jul 21 '16 at 14:15
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    Johns' wife? How many is she married to? – Andrew Leach Jul 21 '16 at 14:17
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    Acoording to what I can find, if you pronounce it, you write it. – oerkelens Jul 21 '16 at 14:30
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    @MichaelSmith Then you should mark this answer or this answer instead, because if that’s what you’re looking for, you’ve asked an exact duplicate. – tchrist Jul 21 '16 at 14:41

You have the rule wrong. The rule is that the possessive and the plural inflexions sound the same, and so if both inflexions are present they are indistinguishable by ear. They do not accumulate: down that road lie Gollum’s rustic fisheses.

The plural of Copernicus is Copernicuses*, which means you add another syllable and a new /z/ sound at the end.

The possessive therefore does the same thing phonologically and so must be written Copernicus’s to match, which is indistinguishable in sound from the plural Copernicuses.

That’s why the plural of farmer is farmers, which sounds exactly the same as farmer’s It’s also why the possessive plural is farmers’, which is indistinguishable in sound from farmers and farmer’s.

  • I’m of course talking English here. If it were Latin, then the plural of Copernicus would be Copernici. Then again, the possessive would then also be Copernici, and so the possessive singular and the plural would still be the same, just like how in English they are the same, at least aurally. Latin has its own possessive plural Copernicorum, so belonging to a bunch of Copernici. English has no special plural possessive, however, and so we would talk about all of the many Copernicuses’ various individual achievements.
  • Ah, it's been a while since I've seen one of your very welcome answers. +1. – Dan Bron Jul 21 '16 at 14:29
  • Thanks for including the addendum about the Latin; it was very interesting – vpn Jul 21 '16 at 15:27

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