Yawning

Yes, a yawn could indicate tiredness, Bernal says. But it can also be associated with moments of stress, so look for context clues to figure out what your dog’s facial expressions really mean.
Lip-licking

A dog that’s licking its lips can be communicating a desire to submit to its human, Bernal tells us. Or it could indicate anxiety or dehydration, depending on the context. If nothing anxiety-provoking is happening at the moment, consider it a positive form of doggie communication – and make sure your pal’s water bowl is full!
Now you might want to know why your dog licks its paws.
Smiling or grinning

Yes, dogs smile, although it doesn’t necessarily signify happiness, contentment or agreement. When a dog lifts its lips to show its canine teeth and incisors, it’s a sign of excitement, says Bernal. This makes sense when you consider that pups tend to smile while out on walks or romping with pals at the dog park. A grinning dog face could also be a sign of submissiveness, but that’s usually when a dog is signalling to other dogs, not humans.