All depend on the extent to which humans can curtail climate change by limiting greenhouse gas emissions in the future. What does the underlined word mean?

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