Or, to put it another way, plurals don't need apostrophes. I talked last week about the many ways in which different words form plurals, BUT APOSTROPHES ARE NOT ONE OF THEM! Sorry to shout but this really does need emphasis.
Apostrophes mean two things:
Possession - On Look and Read, the BBC Schools TV programme where I was Reading Consultant for eighteen years, we had little animated songs to teach aspects of learning to read. There was one that went like this:
'That bike belongs to Tim, it must be Tim's
That car belongs to Sid, it must be Sid's
That bike is Tim's
That car is Sid's.
If a thing belongs, use apostrophe s.'
Straightforward, if a bit non-inclusive. But what if the name or noun ends in "s"? This car belongs to Jess - it must be Jess's. Or "It's Jess's car." The bike belongs to James - it must be James's. Or "It's James's car."
Some people think it's more elegant just to use the apostrophe and leave the possessive s off when dealing with a name or noun ending in an s sound already: It's James' bike. But I bet they never say it that way even if they write it so.
Plural possession - Hang on - didn't she say apostrophes have nothing to do with plurals? No, I didn't. I said they don't mean plural. And they don't.
When I was eleven I won a scholarship to a single sex private school in Dulwich. It was called James Allen's Girls' School, universally known as JAGS. I have always said it was a lesson in punctuation in itself. The apostrophe goes before the s in Allen's because the school was founded by (i.e. belonged to) the one man, James Allen. The apostrophe goes after the s in girls,' because the school was for girls, plural.
Where are the girls' bikes? Where are the witnesses' statements?
Omission - Look and Read had a song for that too and this one is on YouTube: https://www.youtube.com/watch?v=tj7IdnwcrV8
"I'm an apostrophe
Come and take a look at me.
I'm not a comma,
I'm not a full stop.
Don't put me on the line.
I go at the top!
See how we use an apostrophe
To shorten what you say to me..."
Followed by examples like I'm, can't, don't and that's, showing how I am, cannot, do not and that is lose a few letters and replace them with an apostrophe.
So that's it. Apostrophes mean possession or omission. THEY NEVER MEAN PLURAL.
Sorry; I'm shouting again.