A facial expression comprised by flexing the muscles of both ends of one's mouth, often showing the front teeth, without vocalisation, and in humans is a common involuntary or voluntary expression of happiness, pleasure, amusement, goodwill, or anxiety.
"When she heard the surprising news, her face broke into a wide smile that revealed her front teeth."
In plain English: A smile is a happy expression on your face where you show your teeth by curving your lips upward.
"Her warm smile made everyone in the room feel welcome."
change one's facial expression by spreading the lips, often to signal pleasure
"After hearing the good news, she smiled broadly as her eyes crinkled with genuine happiness."
To have (a smile) on one's face.
"She smiled brightly when she saw her friend approaching from across the room."
In plain English: To smile as a verb means to curve your lips up into a happy expression.
"She smiled when she heard the good news."
Usage: Use this verb to describe someone actively displaying happiness or friendliness by curving their lips upward, rather than merely possessing the facial expression passively. It often functions as an intransitive action where no direct object is needed, such as "she smiled at him."
The word "smile" traveled into English from Middle Low German and its earlier Germanic relatives. While it originally meant to smile, its ancient roots in Proto-Indo-European also carried meanings like to laugh or feel glad.