What is the greek word for goodbye?

There isn't one single Greek word that perfectly translates to "goodbye" in English, as the best choice depends on the context. However, here are a few options and when they might be used:

* αντίο (antio): This is probably the closest single-word equivalent and is widely used in most situations. It's a versatile farewell.

* γεια (ya): More informal, like "bye" or "hi" in English. It can be used as both a greeting and a farewell.

* Longer phrases, such as καλό ταξίδι (kaló taxídi) ("have a good journey") or καλήνύχτα (kaliníxta) ("good night") would be used in specific circumstances.

So, while αντίο (antio) is a good general answer, the most appropriate word depends on the situation and your relationship with the person you're saying goodbye to.