Have you heard back from them?请问这里的back是什么词性?当回信讲?

Have you heard back from them?请问这里的back是什么词性?当回信讲? you have just come back from your hometown just 的词性是什么 为什么放在 Have you heard anything back from Mr. Mu on Bo Zhu? I have not heard back from you yet and I see that the purse Jack is back home from the zoo.这句话中back的词性是什么,home还是副词吗?还是说词 I have them shipped back from China every time I go back. you are back from china中文是什么 you're back from Have you come back to 的中文意思是什么啊? send back to中back的词性 have you get back have heard that love to come back