It is generally agreed that "Hello" is an appropriate greeting because if you entered a room and said "Goodbye," it could confuse a lot of people

Good morning starshine, the Earth says hello!

And then, just as Wilbur was settling down for his morning nap, he heard again the thin voice that had addressed him the night before.
"Salutations!" said the voice.
Wilbur jumped to his feet. "Salu-what?" he cried.
"Salutations!" repeated the voice.
"What are they, and where are you?" screamed Wilbur. "Please, please, tell me where you are. And what are salutations?"
"Salutations are greetings," said the voice. "When I say 'salutations,' it's just my fancy way of saying hello or good morning.

I bring you very warm personal greetings from President Clinton, and he is very much looking forward to his visit in June,

Woe unto you, Pharisees! for ye love the uppermost seats in the synagogues, and greetings in the markets.

Do not let that trouble Your Excellency; perhaps the greetings are intended for me.