colour or color, criticise or criticize ...

[Alceste]

[Mimo]

My eldest son, aged 14, learns both at school : English and American forms for these words... even if it is well known that american forms are more common than the English ones...

Mimo

[Jacques]

American English was believed to separate from British English after 1776 and after WWI, but now both languages are merging.

Is is always in favor of American English? Are there cases where British is winning?

If the British start re-using "fall" for "autumn", then older British is winning.

[Charles]

Another word that betrays the origin of the writer is centre / center .
The British centre is usually the heart of the town, whereas the American center is often a sports ground (as I have been led to understand).

[guillaume]

In America center is much used with other words like shopping, sport, convention and exhibition. Those functions are mostly located outside the city, on large grounds, in order to accommodate more car without much traffic jam. The use of horizontal surface is very typical.
In Europe it is common to keep those activities in the center of the city, near the train station and other facilities, for much people don't rely on car.
As in Québec we have North-American habits, we have the same kind of meaning in French with “centre” as place for meeting, either in the center of the city or not (generally not). English Canadiens would use either center or centre, as a reminiscent of British spirit. Might be a good way to keep names bilingual...

[Twister]

In my opinion the usage doesn't determine whether one form or the other should be learned. You should also take into consideration the register: American is more commonly used for the informal communicative purposes, whereas British English still retains this "sophistication" of the upper-class dialect. If you take a closer look at the language that film protagonists use, you will see that uneducated, informal, friendly, "cool" characters use the American slang (for instance, Shrek and his companion).
Personally, I had to learn both forms, but it was absolutely clear that a student of English Philology has to know them. Nevertheless, I do consequently use British spelling and pronunciation.

[deadxkorps]

But there's also the fact that American English speakers outnumber by far British English speakers... So as far as internet is concerned, it is obvious that one form will win over the other... Which I think has nothing to do with the "who should win" question...

Anyway, there's also the Toward / Towards. Towards is normally British but I've noticed that nowadays, even British speakers begin to write "toward".

I think American influence is so powerful, especially in the UK, that they eventually manage to impose *their* forms on the the others. Especially since British youngsters find it waaaaay cooler to speak the American way. (exemple : Saying "Fu*k you" instead of "Bugger off" etc etc)

[Twister]

I wouldn't be so sure. There is a marked tendency nowadays to preserve national identity and I'm observing, at least here, that the influence of the American slang is declining. Perhaps when you're an adolescent, you're more influential and strive for acceptance by all means, but then, people grow out of this. This "cool" language, which might seem so normal when you're fifteen, sounds rather silly and pretentious when you're older. Moreover, the lifestyle, which the Americans were supposed to represent, is also slowly stripped of those positive qualities.
We'll see, what will happen.

[Gaillimh]

I would add some further differences:
defence/ defense
offence/ offense
programmes/programs

and those:
theater/theatre
center/centre

and those concerning vocabulary:
pavement/sidewalk
railroad/railway
wheat/corn
shop/store
films/movies
...

Of course, more and more typically American spellings or American loans are used in the UK. This should be related to the expanding use of the Internet (as a csq, American and English youngsters can write to one another). As far as Phonetics is concerned, I really think that the increasing in pronunciation loan AND also loan words is chiefly due to the expansion of TV programmes.

Most English films come not from Britain but from America. The cartoons children watch on TV are American ones, with American accents. That explains why a 5-year-old boy may say /i:ther/ insted of /aithe/ (either) for instance.

[Pascalitsa]

[Jacques]

[Poisson rouge]

I do agree with you Twister, I don't think American English is "invading" UK. There is an influence, through films, music, etc, but I personnaly don't think British English is going to disappear. As you said it's ok when you're 15, but if you are a student for example, you just don't speak like that (and can't, as it certainly wouldn't be accepted in essays). We Brits are proud of our language, and there has always been a "war" between British and American "way of life", and I think language is part of it: language defines a national identity! And the Brits wouldn't want to sound American...

[Plasticine]

In english it's said afterward while in American engish it's said afterwards. (not such a difference)
But there are many grammatical differences between english and American english like to take (breakfast, shower, ect...) and to have (breakfast, shower, ect...)

[nick27]

There're plenty of differences like these. Even the structures of the sentences tend to be different depending on where you are. For instance :
the Americans say « You seem to be very tired » where the British would say « You seem very tired ». This is not a big difference and I acknowledge some Britons might say « You seem to be very tired ,» too but if you go look up on Google you'll see the American way of saying it is much more used than the British one

By the way « if you go look up ... » is an americanism, too (if you go and look up )

[BlindPew]