Excerpt from Eats, Shoots and Leaves by Lynne Truss, plus links to reviews, author biography & more

Meanwhile, the full stop is surely the simplest mark to understand – so long as everyone continues to have some idea what a sentence is, which is a condition that can't be guaranteed. As the original "point" (so called by Chaucer), it appears to occupy a place in our grammar that is unassailable. Every time the sentence ends, there is a full stop (or a full-stop substitute such as the exclamation mark or the question mark). As easy as that. If you resort to full stops all the time, by the way, and don't use anything else, and keep to very short sentences, people who have read H. W. Fowler's The King's English (1906) will accuse you of "spot plague" and perhaps also assume you are modelling yourself on Ernest Hemingway, but the good news is you can't go wrong grammatically. The American name "period", incidentally, was one of its original English names too. Just as the word "comma" originally referred to the piece of writing itself (rather than the mark that contained it), so "period" referred to a longer piece of writing. Shakespeare called the full stop a period in A Midsummer Night's Dream when he described nervous players "making periods in the midst of sentences". This was on the occasion of one of the first (and unfunniest) scenes of someone wrecking the sense of a speech by putting the full stops in the wrong place:

We do not come as minding to content you,
Our true intent is. All for your delight
We are not here.

William Shakespeare,
A Midsummer Night's Dream, Act V, scene i

Ho hum. But we should not be complacent even on behalf of the robust and unambiguous full stop. Young people call them dots, you know. They are now accustomed to following a full stop with a lower-case letter and no space. Ask them to write "seven-thirty" in figures (7.30) and they will probably either put a colon in it (because their American software uses a colon for 7:30) or write 7-30 or 7'30. Meanwhile, the illiterate default punctuation mark is nowadays the comma, which gives even more cause for alarm:

The tap water is safe to drink in tea and coffee, however, we recommend using bottled water for drinking, it can be purchased very cheaply in the nearby shops.

Sixty years ago, when he wrote Mind the Stop, G. V. Carey gave just one paragraph to the apostrophe, because there was so little to say about it. "If only all marks were so easy," he sighed. But this was in an age when people had been taught the difference between "Am I looking at my dinner or the dog's?" and "Am I looking at my dinner or the dogs?" What I hope will become clear from this book is that one can usefully combine a descriptive and prescriptive approach to what is happening to this single aspect of the language. The descriptive sort of linguist tends to observe change in the language, note it, analyse it and manage not to wake up screaming every night. He will opine that if (say) the apostrophe is turning up in words such as "Books", then that's a sure sign nobody knows how to use it any more; that it has outlasted its usefulness; it is like Tinkerbell with her little light fading, sustained only by elicited applause; it will ultimately fade, extinguish and die. This is a highly sane and healthy point of view, of course – if a little emotionally cool. Meanwhile, at the other end of the spectrum, severely prescriptive grammarians would argue that, since they were taught at school in 1943 that you must never start a sentence with "And" or "But", the modern world is benighted by ignorance and folly, and most of modern literature should be burned.

Somewhere between these positions is where I want us to end up: staunch because we understand the advantages of being staunch; flexible because we understand the rational and historical necessity to be flexible. In Mind the Stop Carey defines punctuation as being governed "two-thirds by rule and one-third by personal taste". My own position is simple: in some matters of punctuation there are simple rights and wrongs; in others, one must apply a good ear to good sense. I want the greatest clarity from punctuation, which means, supremely, that I want apostrophes where they should be, and I will not cease from mental fight nor shall my sword sleep in my hand (hang on, didn't "Jerusalem" begin with an "And"?) until everyone knows the difference between "its" and "it's" and bloody well nobody writes about "dead sons photos" without indicating whether the photos in question show one son or several. There is a rumour that in parts of the Civil Service workers have been pragmatically instructed to omit apostrophes because no one knows how to use them any more – and this is the kind of pragmatism, I say along with Winston Churchill, "up with which we shall not put". How dare anyone make this decision on behalf of the apostrophe? What gives the Civil Service – or, indeed, Warner Brothers – the right to decide our Tinkerbell should die? How long will it be before a mainstream publisher allows an illiterate title into print? How long before the last few punctuation sticklers are obliged to take refuge together in caves?

Reprinted from Eats, Shoots & Leaves by Lynne Truss by permission of Gotham Books, a member of Penguin Group (USA) Inc. Copyright © Lynne Truss, 2003. All rights reserved. This excerpt, or any parts thereof, may not be reproduced without permission.