"Hello" is a common and informal greeting. "Hi" and "Hey" are also casual greetings. "Greetings" is a more formal way of saying hello, often used in business or formal settings.
"Good morning/afternoon/evening" is a way to greet someone depending on the time of day. "Welcome" is a way to greet someone who has just arrived somewhere.
"Howdy" is a casual and friendly greeting, often used in the southern United States.
"Sup" is a casual and informal way of saying "what's up".
"Yo" is a casual and informal way of greeting someone and is more commonly used among friends and acquaintances.
