This question has been asked about a million times here. If you want a really comprehensive answer, just take a look at this: http://en.wikipedia.org/wiki/Comparison_of_American_and_British_English Just a few points to add : American and British English are the SAME language. The accents are different, but they are mutually comprehensible. Whereas a French person may struggle to understand some French speakers from Africa or even Canada, this is very rarely the case for English speakers. The grammar is almost identical, and over 95% of the vocabulary is the same. There are a few very small and unimportant spelling differences. Another thing to bear in mind is that, as English becomes more globalised, it is also becoming more homogeneous. In the UK, younger people are adopting American vocabulary and expressions, and to a certain extent even pronunciation, without even realising it. The differences are disappearing fast.

Same language: as is Australian English, Canadian English, New Zealand English etc. Some spelling differences. For example, Australians, New Zealanders, British and Canadians spell CENTRE and THEATRE this way, but Americans change it to CENTER and THEATRE. Canadians use a number of American spellings, for example, TIRE not TYRE. And although their official language website lists TRAVELLING as the correct spelling I do believe a lot of Canadians use the American form TRAVELING. These differences (between Canadians, Australians, British, Irish, New Zealanders, South Africans, etc.) may cause some amusement amongst us, but we all understand each other. It's the same language. Accents can cause problems, but I have NEVER had a problem understanding an American or Australian (with the exception of some teenagers who seem to speak a language of their own!). I HAVE SERIOUS PROBLEMS understanding some of the accents in my own country though. I cannot understand people from Glasgow when they speak quickly, and the people from rural Norfolk, only a few miles from Cambridge, sometimes speak incomprehensibly (to me!)

Apart from having a different accent, some words that are the same are spelt differently for example: Colour (British) is spelt Color (USA) Urbanisation (British) Urbanization (USA)