Here are some common greetings in the US:
Informal:
* Hey: This is a very casual greeting used among friends and family.
* Hi: A more general greeting, suitable for both casual and slightly more formal settings.
* What's up? A friendly greeting that often leads to a brief conversation.
* How are you doing? A polite greeting, but often just a formality.
* Good morning/afternoon/evening: Used at different times of the day.
Formal:
* Good morning/afternoon/evening, [Name]: Used in professional settings and when addressing someone you don't know well.
* Hello, [Name]: A polite and formal greeting.
* Nice to meet you: Used when meeting someone for the first time.
Regional Variations:
* Howdy: A friendly greeting often used in the Southern US.
* Yo: A casual greeting often used in urban areas.
Important Note: It's generally polite to respond to a greeting with a similar level of formality. For example, if someone says "Good morning," you should respond with "Good morning" rather than "Hey."
Ultimately, the best greeting to use depends on the situation and the people involved.