Do dogs smile or laugh?

I know that dogs tend to wag their tails when they are happy but do they ever smile, grin, or laugh to show happiness?
Dogs can smile and laugh.  When a dog is relaxed and its tongue is hovering over its front teeth, this is a genuine smile. [2]  When a dog is playing, it may laugh, which sounds more like panting. [1][2]
Dogs can smile, but it is not the same type of smile that humans give.  [1][2][4]  When humans smile, the corners of our mouth lift up. [1]  Dogs do not have the same type of mouth, so their smile looks different. [1][4]  Instead of lifting the corners of their mouth, dogs will have their mouth open and may be panting, with no facial or mouth tension. [4]  While some dogs will appear to smile if they are showing submission to their human counterparts, this is actually a sign of the dog being in a relaxed muscular state. [4]