Formal:
* "See you later." This is the most common and versatile option.
* "Goodbye for now." This is a bit more formal than "See you later."
Informal:
* "Cheers." This is a very common way to say goodbye, especially among friends. It can also be used to express thanks or agreement.
* "Catch you later." This is another informal option, similar to "See you later."
* "Ta-ra." This is a slightly more old-fashioned way of saying goodbye.
* "Right then." This is a bit more informal than "See you later" and often implies that you are leaving soon.
Other options:
* "Until next time." This is a more formal way to say goodbye.
* "Take care." This is a polite way to say goodbye.
It's important to note that the specific word or phrase you use will depend on the context and your relationship with the person you are speaking to.