A smile is an overall facial expression. That's why eye gaze can also indicate a smile, and even how to straighten your face can also mean a smile.
Smiling is a very pleasant behavior. In a smile, radiated positive feelings and behaviors, friendliness, joy, courtesy, and respect. Smiles not only determine facial expressions, but also make the brain memprodusir endorphin hormone. This hormone according to medical science, has properties that can reduce pain physically and psychically. That's why there is a saying "smile is healthy". Similarly, the muscles that contract when we smile, far less than the muscles that contract when we are angry. So the saying goes, "do not get angry sooner old". A smile has tremendous power. A smile can make us see the world more beautiful. A genuine smile can melt a frozen relationship, encourage a desperate person, brighten up a grim atmosphere, a restless soul sedative. Smiling can be a boost.