Thread count is measured as TPI: threads per inch.  This is a simple count of the number of threads per inch measured along the length of a screw.

Thread pitch is used in the metric system for measurement of screw threads and is called the “thread pitch.”  This is the distance between two thread “peaks” and is expressed in millimeters.  

Note: What is a screw thread? A screw thread, (often referred to as “thread”) is a helical structure used to convert between rotational and linear movement or force and is a ridge wrapped around a cylinder or cone in the form of a helix. Screws are often made of stainless steel, PEEK, polypropylene, nylon or other synthetic materials.