Dogs do smile, but not exactly like humans. Their "smile" is often a relaxed, open mouth with lips pulled back and can indicate happiness and contentment. Dogs may also mimic human smiles, as they are highly attuned to human facial expressions and social cues. Additionally, dogs sometimes show a "submissive grin," which is a way to indicate they are not a threat and to appease their human or other dogs. This submissive smile can look like a toothy grin but is generally paired with relaxed body language. Therefore, dogs do smile in ways that express positive feelings, often linked to their interaction with humans and other social signals, but their smiles can also serve different social purposes like submission or appeasement.