Words are assimilated to greater or lesser degrees. I'd say that au revoir is now English, as I'd expect any competent English speaker to understand it, but it'

Words are assimilated to greater or lesser degrees. I'd say that au revoir is now English, as I'd expect any competent English speaker to understand it, but it's still commonly written in italics and pronounced in a noticeably French accent. Meanwhile, café is fully anglicised and not really registered as foreign at all, but that pesky accent remains in the written form, giving a clue to its soupçon of French (the truly English form of the word is probably caff).