Count() question...

[wxdqz]

Can someone help me with this simple thing.
I searched the forum but no satisfaction there.

I want to count records in a mySQL table like this.

I have 5 entries. defined like this.
#1 thread 1
#2 thread 1
#3 thread 2
#4 thread 3
#5 thread 2

I tried this;
mysql_query("Select count(thread) from forum");

But that just counts the entries (5). I want to count
the thread so it displays 3.
Counts the 3 different threads that is.
hope you understand.

Thanx in advance.