Hi there,
I'm just writing a letter in Microsoft Office Word software and it corrects me when I write "humour" (suggesting "humor"). I looked up this word in my academic dictionary (which is very good one) and there is just "humour" with "u". I'm confused. Is it possible, that if I say just humour (standing alone) is it with "u" and if I say it with any adjective (dark humor) is it without "u"? Otherwise I don't get it :-(
I had very similar problem with word neighbour/neighbor about a month ago and I assumed it's a difference between British and US English; but if so, I don't know why this Office thing corrects me...

Any explanation please?
Thank you very much!