British vs American Spelling
There are differences between the way words are spelled in Britain and the United States. Canada spells words the British way perhaps because it stayed as a British colony longer than the US. The United States broke away from Britain away during the American Revolution (1775 - 1783). Most words are the same however there are some differences.
The Most common ones are the following:
Britain US
Colour Color
Humour Humor
Defence Defense
Travelled Traveled
There are many more examples but this is a start.
If you have any questions leave a comment or send me an email at doug@English-With-Doug.com.