Pitch
Lead
Thread- & helix angle
Crest- & root radius
Major & minor diameter
Effective diameter
Flank clearance angle
Tilt angle
Right & left hand thread
The main menu
The sub menu
The pages
The test
The thread angle is the angle produced between the threads.
For a straight thread, where the lead of the thread and the pitch diameter circle circumference form a right angled triangle, the helix angle is the angle opposite the lead.