Bye bye and So long

So long and bye bye are semantically related. in departure topic. In some cases you can use "So long" instead the phrase "Bye bye" as a noun or a interjection, when it comes to topics like goodbye, farewell statement.

So long noun - A farewell remark.

Bye bye and so long are semantically related. You can use "Bye bye" instead the phrase "So long" as a noun or a interjection.