Formal:
* Greetings: A more formal way to say hello.
* Good morning/afternoon/evening: Used depending on the time of day.
* How do you do? A very formal greeting, often used in more traditional contexts.
* Nice to meet you. Used when meeting someone for the first time.
Informal:
* Hi: A common and casual greeting.
* Hey: A more informal version of "hi," often used with friends.
* Howdy: A Southern greeting.
* What's up? A casual way to ask how someone is doing.
* Yo: A very informal greeting, often used by young people.
* Sup? A very casual, slang greeting.
Other:
* Ahoy: Used by sailors.
* Aloha: A Hawaiian greeting that means "hello" and "goodbye".
* Shalom: A Hebrew greeting that means "peace".
* Namaste: A Hindu greeting that means "I bow to you".
* Guten Tag: German for "good day".
* Bonjour: French for "good day".
* Ciao: Italian for "hello" and "goodbye".
The best word to use depends on the situation and your relationship with the person you're greeting.