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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