For punctuation pedants, a misplaced apostrophe is the cause of much rage. Their blood boils at the sight of this elevated comma being used in the wrong place. Personally, I try to stay mellow about it - after all, I can’t kick a ball in a straight line. Everyone has different skills, right?

But when it comes to business, there’s no excuse for getting the basics wrong. While the odd typo is inevitable, consistently poor spelling, punctuation and grammar will mark you out as unprofessional.

Which is why I thought you’d appreciate this little guide on how to use an apostrophe correctly…

To replace missing letters

This is an easy one, so people usually get it right. When do not becomes don’t, the apostrophe takes the place of the second o. When they will becomes they’ll, it is there in the place of both the w and the i. So far, so simple.

To signify possession

This bit also starts off in a relatively uncomplicated fashion. When Susan buys a book, it is Susan’s book. When the builder makes a sandwich, it is the builder's sandwich.

What if the builder is a really hungry and has two sandwiches? Same deal - the builder’s sandwiches. But what if there are several builders? Now we need to move the apostrophe so that it comes after the pluralising s.

But now you have a choice. Not about whether of not you use the apostrophe, but whether you use the second s. If a plate of sandwiches belongs to a group of builders, they could be the builders's sandwiches or the builders' sandwiches - it's up to you.

The same goes for the Smith family. While Fido might be Mrs Smith’s dog (apostrophe before the s), he is also the Smiths’ dog - the dog belonging to the Smiths as a group - or the Smiths's dog.

If you want a way to decide whether to use the final s, some editors stick with the policy of keeping it for a common noun and dropping it for a proper noun - so you'd end up with the builders's sandwiches and the Smiths' dog.

It's worth noting that if the family's surname ends with an s, you’ll need to pluralise it before adding the apostrophe. So while Mittens is Mr Williams’ cat, she is also the Williamses’ cat. Or technically you could write the Williamses's cat but that's a tad clunky!

Just watch out for irregular nouns, which become plural in a way other than by adding an s or es - like child, which becomes children (rather than childs). If you want to refer to toys belonging to said children, you would say the children’s toys and not the childrens’ toys (because the plural of child is not childrens). Still with me?

Its vs It’s

There is an exception to the apostrophe that signifies possession: it. If a bird of non-specific gender built a nest, said nest would be its nest. So a bird builds its nest, a company looks after its staff and a plant absorbs water through its roots.

The only reason to add an apostrophe to its is if you’re using it as the contraction of it is ie it's. In this case, the apostrophe signifies the missing i, as per rule number one above.

If in doubt, try lengthening its to it is - if it doesn't work, you don’t need an apostrophe. As an example, you wouldn’t say that the floppy disc has had it is day, therefore you should write the floppy disc has had its day, and not it’s day.

Acronyms

For some people, all of this is relatively straight forward. Until they meet an acronym. Then for some reason they decide it’s time to throw the rulebook out of the window, and use an apostrophe before a s that is being used to create a plural, rather than to show possession.

So while they'd never say that one file becomes two file’s, they’ll happily talk about the garage that offers excellent MOT’s, the shortage of ATM’s in town, and how difficult it is to remember so many PIN’s. (Incidentally, this actually does make me feel quite twitchy.)

Remember, unless you are signifying possession (the ATM’s screen or, if dealing with many ATMs, the ATMs’ screens) you don’t need that apostrophe.

Exceptions

I’m fairly certain that the English language was designed to confuse, which means you will always find an exception to any rule.

For example, if you wanted to say that when people’s handwriting is bad, their as often look like us, it’s probably helpful to add apostrophes to make your meaning clear: when people’s handwriting is bad, their a’s often look like u’s.

Likewise, you might want to write about the do’s and don’ts of using apostrophes (even though it’s actually incorrect) - because it’s just clearer than dos and don’ts (which is how it should technically be).

So there we have it. Not all that hard, is it? If you’re still stuck with a particularly tricky punctuation puzzle, email us and we’ll set you straight.

***

Did you enjoy this article? Share it with your colleagues now on Twitter, LinkedIn, Facebook or Google+.