It is worth looking back at some time of the amazing scientific advances we have made in the last few decades. What is not the meaning of the underlined word?

He became rich overnight. What part of speech is 'overnight'?

The nightingale is a singing bird. In this singing is a/an --

I Came home after the rain -----.

The Doctor took the round in the hospital. Here 'round' is a/an ---

Alumni is the plural from of