Happy is an adjective that refers to something or someone that is characterized by joy or contentment.
It is often used to describe a person's emotions or a physical object or situation that has brought joy to those involved. The rules for using happy as an adjective are fairly simple; it is used to describe something or someone that has a positive emotional state. For example, 'I'm so happy to meet you!'
1. 'She had a happy smile on her face.'
2. 'His happy laughter filled the room.'
3. 'The students were so happy to have their teacher back!'