When someone's smiling, they're showing happiness and friendliness on their face. A smile can also be something that happens in the moment.
Smiling is a very common way to show people how we feel. You might see someone smiling when they're happy about good news or when they've had a great time with friends. When you meet someone for the first time, it's often polite to smile and make them feel welcome. Sometimes smiling can be more than just a facial expression - it can also mean that something is going well or turning out better than expected, like when your favorite team wins a game and everyone starts smiling because they're so happy about it.
To have (a smile) on one's face.
Example: I don't know what he's smiling about.
The action of the verb to smile.
Example: Smiling takes fewer muscles than frowning.
That smiles or has a smile.
Example: smiling children
