subject vs. class

Hi,

I have a question on subejct vs. class. I looked up my dictionary, and it says:

A subject is an area of knowledge or study, especially one that you study at school, college, or university.

A class is a course of teaching in a particular subject.

They seemes to be similar. But they have differences in meaning. So I think the usage of them are different.

For example:

I’m taking an English class this semester.
I’m taking an English subject this semester.

I signed up for the class.
I signed up for the subejct.

How many classes are you taking?
How many subjects are you taking?

I would rather use the formers than the latters in those cases. What I think is that subject is not collocated with take or sign up for. What do you think? Do you think the latters are all natural?

However, in some cases like below, I think both ‘class’ and ‘subject’ is okay:

What subject are you interested in?
What class are you interested in?

Are my examples okay? If not, would you please give me some examples of their similarity or differences?

Thanks,
sweetpumpkin

I agree except for the last one. I’d use ‘subject’ only–unless you are discussing specific classes (= course of teaching).