Informal:
* नमस्ते दोस्त (namaste dost): This is the most common and casual way to greet a friend. "namaste" is a respectful greeting, and "dost" means friend.
* हाय दोस्त (hai dost): This is a more modern and casual greeting, similar to "hi friend" in English.
* अरे दोस्त (are dost): This is a very informal and friendly greeting, often used among close friends.
Formal:
* नमस्ते मित्र (namaste mitra): This is a more formal way to greet a friend, using "mitra" which is a more formal word for friend.
Other options:
* शुभ प्रभात दोस्त (shubh prabhat dost): This means "good morning friend."
* शुभ संध्या दोस्त (shubh sandhya dost): This means "good evening friend."
Ultimately, the best way to say "hello friend" in Hindi will depend on your relationship with the person you are talking to and the situation.