This document discusses yarn count systems. It explains that yarns come in different thicknesses and are typically sold based on weight. There are two main systems for expressing yarn count: direct and indirect. Direct systems indicate the weight of a given length of yarn, while indirect systems indicate the length of yarn in a given weight. Common direct units include tex, dtex, and ktex which measure grams per 1000 meters, 10000 meters, and 1 meter respectively. Common indirect units include Nm, Nec, and Nw which measure meters, 840-yard hanks, and 560-yard hanks per gram respectively. The document provides examples and conversion factors between different count systems.