A friend asked me recently to explain where the apostrophe should go in the phrase my parents house. I realised that this is something I’ve corrected many times when editing manuscripts, so it seemed a good subject for a quick tutorial. Here’s an easy way to work it out.
Ask yourself: How many parents are we talking about? If only one (singular), then the apostrophe goes after the word parent:
my parent’s house
meaning: the house of my parent
But if we’re talking about plural parents—mother and father, two mothers, two fathers, any combination of people playing parental roles!—then the apostrophe goes after the plural s:
my parents’ house
meaning: the house of my parents
In summary, to indicate possession:
add apostrophe + s to a singular term
add apostrophe only to a plural term
Where it gets complicated is when the singular term ends in s. There are acceptable variations here, and it becomes a matter of style rather than a rule. I prefer the recommendation of the Style guide for authors, editors and printers (6th edn, John Wiley & Sons, 2002), which is:
apostrophe + s (i.e. no change to the rule above for a singular term)
meaning: the novels of Dickens
meaning: the poems of Burns
For: It’s easy to remember because it’s the same style!
Against: Some people think it looks clumsy.
Feel free to disagree! Here are a couple of alternatives.
Some guides recommend:
For: Some people think it looks neater.
Against: Why complicate things?
Others recommend different styles depending on the number of syllables in the singular term:
more than one syllable: apostrophe only
one syllable: apostrophe + s
For: I can’t think of one!
Against: It looks inconsistent, and why complicate things even further?
There’s yet another variation involving pronunciation (i.e. whether you sound the s or not), but that, in my opinion, is a highly dubious way of deciding which style to use: not everyone pronounces words the same way. So let’s not even go there.
As with any point of style for which there are variations, what’s important is that you choose one (or follow the style set for you) and use it consistently.