Rant ahead: proceed at your own risk

"How important is grammar and when do you break grammar rules?"

Less important than story, character and pacing but a smidge more important that spelling and punctuation? At a guess. An editor can fix unintended grammar gaffs, but if a story is boring or all the characters are thin, you won't have an editor willing to take you on.

The word I want to home in on in that last paragraph is "unintended". If you're aiming at some particular English dialect - Standard US or 18th century Cockney . . . whatever - you don't want to miss.

Quite often, though, when people talk about "grammar", "correctness" and "rules", they're trying to impose some random hierarchy of prestige on the big glorious ragbag of the world's Englishes.

Yes, formal standard English from your home country has its place. It's a good idea to use it in a querying letter to agents and if your publisher's contract doesn't use it, you might be in trouble. If you dispense with all rules of grammar completely and just ramble on repeating a jumble of your favourite words in vaguely connected phrases, you'll never get anywhere.  Sorry, bad example. Where was I?

But the local formal standard is only one of the options. All the dialects, regional, racial and social, all the other standards around the world . . . What riches! What treasure! What bugs me about sticklers for grammar is how often they think (unthinkingly, surely) that their particular variety of English is maximally correct, expressive and elegant and all the others are lazy, degenerate and hard to understand.

Argh.

Here then are my top three peeves about people with peeves about grammar. (I also don't suffer people who don't suffer fools gladly gladly.)

3. They're faking!

People who pretend not understand dialects are sometimes lying. When I was growing up, I heard many, many times that if I said "I int got none" I was really saying "I've got some" because two negatives make a positive. Nonsense. Wrong. I wasn't and they knew I wasn't. They understood the meaning perfectly well. They were faking. And for some bizarre reason, it was a matter of pride to pretend not to understand, as if dodgy comprehension skills were cool. "I ain't done nothing", "I haven't seen any" "We don't need no education" (naughty Pink Floyd) and "Je ne sais pas" have all got two negative bits in them. And they're still negative. To turn them positive you need to change both bits.

2. They don't get that all languages are orderly systems!

I've heard otherwise quite thoughtful people say, straight-faced, that the grammar of some dialect or other is just wrong. A mistake. Doesn't make sense. "My hair needs washed" is good Scottish English but that didn't stop this happening:

English Friend: "My hair needs washing" makes more sense. It needs you washing it. See?
Me: Okay. If we're allowed to add two words to explain why we're right . . . it needs to be washed.
EF: But then you could say "I'm washed my hair right now."
Me: No, I couldn't.
EF: Ha! Why not?
Me: Same reason you couldn't say "Last night, I washing my hair".
EF: Of course, I couldn't.
Me: And no one's allowed to say "mes cheveux ont besoin d'etres laves"?
EF: French people are.
Me: But doesn't it make more sense the way you say it?
EEF: Oh shut up.

1. They think they're the end-point of history. This is the one that really gets on my wick. Here's the argument in a nutshell:

8th Century English: the original and best.

Hwæt! Ic swefna cyst			secgan wylle,
	hwæt me gemætte			to midre nihte,
	syðþan reordberend			reste wunedon!
	þuhte me þæt ic gesawe			syllicre treow

14th century English: very different, still beautiful.

A prentys whilom dwelled in oure citee,  And of a craft of vitailliers was hee.  Gaillard he was as goldfynch in the shawe,  Broun as a berye, a propre short felawe,  With lokkes blake, ykembd ful fetisly. 18th century English: more change but no need to worry IT is a truth universally acknowledged, that a single man in possession of a good fortune must be in want of a wife. However little known the feelings or views of such a man may be on his first entering a neighbourhood, this truth is so well fixed in the minds of the surrounding families, that he is considered as the rightful property of some one or other of their daughters. [grammar stickler happens to be born and learns to speak] 21st Century English: English is doomed and the sky is falling! I got the rap patrol on the gat patrol Foes that want ta make sure my casket's closed Rap critics that say he's "Money Cash Hoes" I'm from the hood, stupid? what type of facts are those? If you grew up with holes in your zapatos You'd celebrate the minute you was having dough In conclusion: language changes. We'll be fine. Rant over.