1. we use formal greeting expression when we talk with teacher,parents, grandmother,grandfather, aunt,uncle, neighbhors,older people, and people who respected. we use informal greeting expression when we talk with friends whi has same age with us,with siblings, and younger people.
2. So we don't look arrogant and so we used to say hello to form character in us to be more friendly and not snobby.
semoga membantu yehet ohorat ^^