It's one of the most misused punctuation marks in the English language and now the English department are launching a competition to find examples of where it's been left out, or used incorrectly. What is it? The humble apostrophe.

Head of English, Mrs Waterman, is hoping that eagle-eyed students will take photographs of any signs, letters, or posters where the apostrophe is being used incorrectly. The person who finds the best example will win a £10 book token.

Here's a quick guide, just in case you need your memories jogging:

• Use one if there's a letter or letters missing:

Eg I will becomes I'll, I do not becomes I don't

• Use one to indicate possession:

Eg The cat's tail, the school's logo, the book's cover.

Remember that the possessive form of it does not have an apostrophe The cat cleaned its paws and the hen laid its egg are both correct statements – you wouldn't put an apostrophe in ours, yours or hers, so there's no reason to put one in its.

• Remember, if there are more than two things then you have to move the apostrophe after the s:

eg: The cats' tails, the schools' logos, the books' covers.

• And the golden rule of apostrophes is never, ever use them to indicate plurals.

You'll find lots of examples of these on any High Street in Britain. Signs proudly proclaim 'MOT's here, Apple's for sale and 1000's of prices reduced' when we all know that they should read MOTs, Apples and 1000s.

So, what are you waiting for? Get spotting and email your entries to Mrs Waterman. The best will be put on the website as examples of how not to punctuate!

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