What are natural and correct words to express these situations?
When I was taking a class, I didn't pay attention to the teacher's speaking.
There are two situations when I didn't pay a attention to others' talking
1. My mind was blank and I didn't think about anything.
2.I was thinking about other thing. For example, when the teacher was talking about business, I was thinking what dishes I gonna to eat.
How do you say these mental status in daily life? I wanna know how to express it naturally, thanks! :)