discussion or discussions

[guoguohu]

I have been confused by the use of discussion for a long time, whether in the singular or plural form?

Can I say:

1, I am involved in discussions with Jack...
2, We had a good discussion, or We have good discussion, or we have good discussions.

[mayita1usa]

The word discussion is just like any other noun:

1, I am involved in discussions with Jack...

This means you are having more than one discussion with Jack over a period of time.

2, We had a good discussion, or We have good discussion, or we have good discussions.

a. We had a good discussion. = We had one discussion, and it was good.
b. We have good discussion. This is ungrammatical.
c. We have good discussions. = We have good discussions on a regular basis (simple present = habitual action), thus more than one discussion in total.

[guoguohu]

Thanks,mayita1usa. You reply is really appreciated.