There are two occasions when you need an apostrophe:
To show that something belongs to something else.
The designer’s mouse The communications director’s heart attack The finance director’s budget
If you are using plurals, then the apostrophe comes after the s:
The designers’ mice (because there is more than one designer) The communications directors’ heart attacks (because there is more than one communications director) The finance directors’ budgets (because there is more than one finance director)
When there are letters missing from your words.
I’ll be late home again dear (I will be late home again dear) He’s the best writer by far (He is the best writer by far) This fish’s seen better days (This fish has seen better days) We’d’ve been better off with the pasta (We would have been better off with the pasta)
Here’s the exception that proves the rule.
When you use the word its to mean that something belongs to it, you never use an apostrophe.
The dog took leave of its senses The umbrella had a mind of its own
The only time that it’s has an apostrophe is when it is short for it is.
I'm no stickler for textbook syntax - how dull would it be if every organisation used the same language and tone of voice? And how hard to tell the difference between one and another?
The English language is constantly evolving and conventions that were frowned upon just a decade ago are now considered acceptable, even for high-level corporate communications.
Short sentences, for example. Even sentences without verbs. To boldly split infinitives is, for many, now no problem whatsoever. And starting a sentence or a paragraph with ‘And’ is commonplace in environments including the leader columns of several broadsheet newspapers.
However, there are some things that you just can’t get away with and which will seriously undermine the credibility of your communication. Poor spelling is one, so consult a dictionary if possible or use a spell-check as a last resort (Microsoft is not infallible, especially if you’re writing English English or Canadian English as opposed to American English).
David Mitchell has a good take on this:
The incorrect use of punctuation is the other big no-go area. It does make a difference, as is clear from the examples below. Apologies if you’ve seen this before, but it does make the point well.
Dear John, I want a man who knows what love is all about. You are generous, kind, thoughtful. People who are not like you admit to being useless and inferior. You have ruined me for other men. I yearn for you. I have no feelings whatsoever when we're apart. I can be forever happy - will you let me be yours? Gloria
Dear John, I want a man who knows what love is. All about you are generous, kind, thoughtful people, who are not like you. Admit to being useless and inferior. You have ruined me. For other men, I yearn. For you, I have no feelings whatsoever. When we're apart, I can be forever happy. Will you let me be? Yours, Gloria
This section is for everybody who's ever wondered about an apostrophe.