"再见卡西" means "goodbye, Cassie" in Chinese. It is a way to say goodbye to someone named Cassie.

The phrase "goodbye" comes from the Old Engpsh phrase "godbwye," which means "God be with you." It is used as a way to bid farewell to someone.

Here are some examples of how "goodbye" can be used in a sentence:

"Goodbye, it was nice meeting you." (再见，很高兴见到你。)
"I'll see you later, goodbye." (我们待会儿见，再见。)
"Goodbye, have a safe trip." (再见，一路平安。)

Note: In Engpsh, it is more common to use the phrase "goodbye" to say farewell to someone, rather than using someone's name. It is more common to say "goodbye, Cassie" rather than "再见卡西."