>>I wanted to search by 'categories' (or 'category') in VFP forum. First I tried to search by this keyword and known people, then just by this keyword only in the default time frame. Every time it returned 0 results. It would be very hard to believe that the word 'categories' never was used in that forum during this period of time.
>
>To me, with the default search criteria, it gives 55 for categories in 293 for category.

Try

search by
'category'
From Berezniker
To Litvak

-----------
Gives 0

Then remove both of them and re-try.
Gives 0 again.