Note: Troy and I recommend only products that we have tried and tested. These include the popular spelling software Ultimate Spelling.*
On this site, we use British English (we are Australian, after all!) American spellings are included in spelling lists, though, and all the software we promote here works with either British or American spelling and vocabulary.
It can be quite confusing when trying to communicate with someone from another English-speaking culture at times. You may think you're speaking the same language, but in many ways you're not! Apart from some major spelling differences, there are also differences in meaning for some words. For example, in England a biscuit is what Americans call a cookie, and in America a biscuit is what they'd call a scone in England, which if nothing else can make tea time a distressing experience if you're not prepared!
While it may not seem that way at first, American English and British English have come from a common source. The Pilgrims took Elizabethan English over to the new colonies, and there it started to change — or not. The word fall is actually an Old English word for the season. Over time fall fell out of use in England, being replaced by autumn, but it was retained in America. The same goes for gotten. This word was used in Old English, travelled to America with the colonists, and then fell out of use in England.
American spelling tends to be simpler than British spelling, which in general retains more of the original spelling of a word. Words that have come from French, for example, will retain their French spelling — for example omelette is the French and British spelling for this tasty dish, while in America the spelling has been simplified to omelet.
Here are the main spelling differences between the two countries:
|-our||-or||flavour and flavor|
|-re||-er||theatre and theater|
|-ise||-ize||organise and organize|
|-yse||-yze||paralyse and paralyze|
|-ogue||-og||catalogue and catalog|
|ae and oe||e||amoeba and ameba|
Double letters are often used differently between the two countries, with American words tending to drop double letters, and British words tending to favour them. For example, counsellor and counselor, travelling and traveling. But there are also examples where the opposite holds true, and American English includes double letters that aren't used in England: enrolment (UK) and enrollment (USA), fulfil (UK) and fulfill (USA).
The main lesson to be learned here is that all varieties of English are just that — varieties. Each has developed regional differences over time, evolving to the dialects we use now (which are still in the process of change); there is no one "correct" version! Just remember to know which version of English you need to write in, become well-versed in its spelling and vocabulary conventions, and don't be judgemental when you come across differences.
*Troy and I have agreed to receive a commission from some sales of Ultimate Spelling because we are happy to endorse that software.