I could equally well have written greengrocer's as greengrocers', because it's up to me whether I mean one or several. This is all about meaning and clarity, not obfuscatory rules. (Yes, I know, we could probably manage without apostrophes at all, but since we have them, let's get 'em right.)
Several of you have asked for a post on apostrophes. Oooh, the pleasure! I haven't done this since I was an English teacher. Apart from the times I taught my daughters. Forcibly. While serving them fish fingers.
By the way, it will be embarrassing if there are typos in this post, especially if they are apostrophe-related! But I can't check it properly until it goes public, and I'm busy surrounded by boxes and may not have internet access. Fingers crossed...
First, forget about "before the s or after the s". We will not be thinking like that, because that way confusion lies. The letter s has absolutely nothing to do with apostrophes. OK? Thinking of s is what has led so many astray.
1. ABBREVIATION - WHEN TWO WORDS BECOME ONE or when something is missed out of a word (though many such omissions are nowadays not represented by apostrophes)
- didn't, can't, mustn't etc - you know this, and I don't need to explain oddities like won't
- It's a lovely day - BUT NB NB NB NB NB: it's ONLY HAS AN APOSTROPHE WHEN SOMETHING HAS BEEN MISSED OUT, ie when it stands for it has or it is. NEVER ELSEWHERE
- The dog's going to eat its dinner - because dog's stands for The dog IS going...
Nowadays, generally speaking, you do not normally need an apostrophe to denote letters missed from the beginning or end of a word, but you do when TWO become one, such as can't - originally can not
In the old days, any missing letters needed to be indicated by either an apostrophe or a full-stop, but not any more. For example, 'phone is now just phone. (There's nothing wrong with 'phone, but it's not needed.) Photo would certainly not be photo'. Therefore, photos* would NOT have an apostrophe. If in doubt, leave it out. These vagaries are a matter of common practice.
*I don't know why this troubles people but please remember that you do NOT just add an apostrophe to denote a plural. The s does that all by itself. This is the problem that greengrocers have. Apples, bananas, peas, etc. No apostrophes. Not unless you're selling the apples' possessions.
CD is one that gets people tangled. Originally it would have been C.D. and you could still write this. Would you say CD'? No, so don't write CD's. (You'd write the CDs' cases though, following the possession rules below - as in the cases of the CDs.)
The most important thing to realise with plurals is that if you would not have had an apostrophe for the singular, you do not for the plural. Because apostrophes play no part in forming a plural word.
20s, 1960s, 80s etc do not have an apostrophe because there is no abbreviation going on.
Some unusual abbreviations, such as 'em for them, would have an apostrophe, simply as a favour to the reader, who might otherwise be confused.
To repeat: nowadays, generally speaking, you do not normally need an apostrophe to denote letters missed from the beginning or end of a word, unless it's required for clarity, but you do when TWO become one, such as can't - orginally can not.
2. POSSESSION - ONLY WHEN THE "POSSESSOR" COMES IMMEDIATELY BEFORE THE THING POSSESSED.
And the only thing to remember about the position of the apostrophe is that it comes immediately after the "possessor". So, if the possessor is plural, put the apostrophe after the plural form.
The dogs' dinner - the things possessing the dinner are the dogs (more than one dog) so the apostrophe goes after the dogs.
If you remember to think "after the possessor", you won't have a problem with, for example, the Joneses' house = the house of the Joneses. The Joneses are the possessors.
EXCEPTION. These words never, ever, ever have an apostrophe, even though they look as though they should**:
Never. Got it? Don't worry about why - just remind yourself that the word mine doesn't have an apostrophe so why should theirs etc? What, because there's an s at the end of theirs? So? We're not thinking about s, remember? S has nothing to do with apostrophes. As I said.
And remember: it's ONLY has an apostrophe for abbreviation - it is or it has
** Technically, these are not even exceptions: in fact, since the object possessed does not come immediately after the word, there's no need for an apostrophe, within the rules. You don't say yours house, do you?
EXTRA POINT. Sometimes you have to notice that the "thing possessed" is omitted, or "understood". For example, I'm going round to Jane's. This has an apostrophe because we mean Jane's place or Jane's house. Another example would be, This is Sally's, not Joan's, book.
CAUTION - be careful to remember the rule with irregular plurals. This is another reason why you must focus on "after the possessor". For example, the children's party or the people's princess - both follow the rule as long as you are not doing that "before the s or after the s thing."
That's it in terms of rules. But of course, that's not quite the end....
A few examples:
1. three weeks' time - because we mean a period of time of three weeks BUT we say in three weeks with NO apostrophe
2. for goodness' sake - because it is for the sake of goodness
3. Accounts Department does not need one, because Accounts is being used as an adjective, describing the department, not indicating possession
4. three hours late - does not need one, because late is not a noun and can't be said to be owned*** by anything.
[***Thanks to eagle-eyed Dave Bartlett for correcting my confused brain there.]
Sometimes it's entirely up to the person creating the phrase. For example, the people of The Writers' and Artists' Yearbook decided that they meant many writers and artists; but the people of The Writer's Handbook decided to refer to one writer. Both equally correct.
And there are times when it comes down to usage and all you can do is look the phrase up on a reputable website and see what the experts say: there's no way I can go through everything here. If in doubt, check.
Do you want to do a quiz? There's one at the bottom of this article here, which also, I see, gives a clear list of apostrophe rules. Between my explanations (especially the "after the possessor" rule) you should have it cracked. There's some nifty footwork on gerunds, too.
Now, I know I haven't answered every possible question, but it would get too bitty. Get your head round the rules first and use sensible internet searching for individual phrases that pose you a problem.
Here are some more resources that seem good at a quick glance:
I also just came across this recent Litopia podcast - I haven't listened but it's Eve Harvey so it will be good.
That's it. You're armed. Go out and prepare to laugh at greengrocers.