Trapezoidal threads are defined as follows by ISO standards:
Tr8x8
where Tr designates a trapezoidal thread, 8 is the nominal diameter in millimeters, and 8 is the pitch in millimeters. When there is no suffix it is a single start thread. If there is a suffix then the value after the multiplication sign is the lead and the value in the parentheses is the pitch. For example:
Tr8x8(P2)
would denoted 4 starts (as the lead divided by the pitch is 4), 8mm diameter, 8mm lead and 2mm pitch.
Modified from:
https://en.wikipedia.org/wiki/Trapezoidal_thread_forms