In the first two “Functional Phrases” lessons you practiced greetings. This lesson you will practice what to say when you leave. There are both polite and casual things to say.
Goodbye.
Goodnight.
Farewell.
Take care.
See you tomorrow.
See you later.
See ya!
“Farewell” is very final sounding, when maybe you won’t meet again. “See ya!” is very casual and friendly.