thousand people

There were thousands of people joining in the parade.

Another alternative (different meaning):

(A) There were at least a thousand people joining in the parade.

Can I say,

(a) There were thousands people joining the parade. (must "thousands of people" ?)

Nope. you've got to use ' thousand' without s even though a figure is put in front.

eg. There were 3 thousand people joining in the parade.

Sorry, i'm not very clear. Can you correct my sentence?

Hi VT

You can say any of the following:

- There were a thousand people in the parade.
- There were one thousand people in the parade.
- There were half a thousand people in the parade.
- There were 5 thousand people in the parade. (You can replace '5' with any number.)
- There were thousands of people in the parade.

There were thousands of people joing in the parade.

I got a question here. "joining" must go with "in"?

The word 'in' is optional in your sentence.

In your sentence, the meaning seems to be that each of the thousands of teams slowly joined the parade. Your sentence doesn't mean that the thousands of teams were already in the parade. Is that the meaning you intended?

Thousands 'of' .....
The 'of' is required (assuming we want things to sound mainstream).

Can I say,

(a) There were one thousand of people ...