good-bye ： 口语中的普通用词，是"Good be with you"的缩略形式，多用于亲友暂时离开的情景。
英汉词典释义
interj.
再见!
Good-bye then!Mind how you go!再见了,路上小心！Fran slipped the catch on the door, then turned to say good-bye.弗兰拉开门闩，然后转身说“再见”。Good-bye,old chap,I’ll see you on my return.再见吧,老伙计,等我回来再见面。
n.
告辞;告别
I must say good-bye now.我现在得告辞了。If you lend him money, you can kiss it good-bye.如果你借给他钱,你就甭想他还你。