Formal:
* Habari yako rafiki yangu? - This is the most formal way to greet a friend, meaning "How are you, my friend?"
* Shikamoo rafiki yangu. - This is a more respectful way to greet someone older than you, meaning "May you be strong, my friend."
Informal:
* Jambo rafiki! - This is a casual greeting, meaning "Hello friend!"
* Sawa rafiki! - This is a very informal greeting, meaning "Alright friend!"
* Mambo rafiki! - This is another casual greeting, meaning "What's up friend?"
Even more informal:
* Hee rafiki! - This is a very casual greeting, meaning "Hey friend!"
* Yo rafiki! - This is a slang greeting, meaning "Yo friend!"
Note: When addressing someone by name, you would add it after "rafiki," for example, "Habari yako rafiki John?" or "Sawa rafiki Mary?"
The best way to choose the appropriate greeting depends on your relationship with the person you are greeting and the context of the conversation.