But quite a number of english speaking individuals do not seem to know how, as can be seen by the number of errors in shop signs and advertisements. Some of the worst culprits are supposedly greengrocers, thus the expression the "greengrocer's apostrophe". Signs can often be seen boosting juicy pear's, savory apple's or the best banana's . Greengrocers however are not the only ones to get it wrong. Here are a few more real world examples of incorrect utilisation, english writers and translators take note:

New CD's just in.

Menu's printed.

Ideal for heaters, lighting, TV's, radio's and other widgets.

Open Sunday's.

It is so noticeable that The Apostrophe Protection Society was set up in 2001, as an association with the aim of chasing up examples of misuse and reminding people of the rules for proper usage of apostrophes.

For sure it is not surprising that foreign speakers have troubles with the apostrophe, if the American or British can't get it right!

So what is the rule? It's really quite simple.

An apostrophe should be used in a couple of cases:

1. to indicate missing letters:

I don't know the answer (I do not know)

It's really quite ordinary (it is)

I'm afraid I can't make the meeting ( I am afraid ? I cannot)

2. to denote possession : the cat's food, the president's secretary, the company's policies, our competitor's promotion

Note that:

* In the plural the possessive apostrophe is placed after the ?s:

the cats' food (more than one cat), the companies' policies (more than one company)

* An apostrophe is not used with "it":

This is in its best interest

It is its best offer

* What about names that end in ?s?

There is no hard and fast rule here. It is usual to add ?'s after the first ?s, for example:

Mr Jones's speech, St James's Street .

However it has also become accepted practice to simply add an apostrophe ( Dickens' novels ).

An apostrophe is NEVER used when the ?s simply indicates the plural form of a noun!

Hence: the greengrocer sells "juicy pears, tasty apples and the best bananas", and the other examples of incorrect usage given at the beginning of this article should read:

New CDs just in.

Menus printed.

Ideal for heaters, lighting, TVs, radios and other widgets.

Open Sundays.

One last point: be careful when using your and you're. Confusion is easy, as they sound exactly the same.

Your is possessive: this is your desk

You're is a contraction of "you are": you're right about that policy.

And be warned ? tracking down examples of wrong usage of apostrophes can become quite habit-forming!