Twisting is one of the purposes of spinning, and the amount of twisting is an important indicator of yarn performance, usually expressed as twist. Twist refers to the number of turns per unit length of yarn (i.e., the number of turns). The unit length varies depending on the type of yarn, and its measurement unit can be expressed as "twist/10cm" or "twist/m". The former is used for cotton and cotton type chemical fiber yarns, and the latter is used for twist measurement of worsted wool and chemical fiber filament yarns. Twist affects yarn strength, stiffness, flexibility, elasticity, shrinkage, and other indicators. As the twist of the yarn increases, its strength increases, but the twist cannot exceed a certain value, otherwise its strength will decrease instead, which is called the critical twist of the yarn. The critical twist of yarns from different materials is different. The softness, elasticity, and shrinkage of yarns are also closely related to twist. Generally, on the premise of meeting the strength requirements, the smaller the twist of the yarn, the better, because increasing the twist will make the yarn feel hard, reduce elasticity, and increase shrinkage, which is why filament yarns are generally not twisted or less twisted as much as possible. In addition, twist also has an impact on the volume, weight, and diameter of the yarn, and twisting increases the tightness of the yarn. Within the range, the volume and weight of the yarn increases with the increase in twist, while the diameter of the yarn decreases with the increase in twist, resulting in changes in the coverage and comfort of the fabric.

In summary, yarn twist should be selected based on different fabric uses. If the warp yarn needs to have higher strength, the twist should be larger; Weft yarns and knitting yarns need to be soft and have a smaller twist; Yarns for woven and knitted pile fabrics should have a smaller twist to facilitate pile formation; Thin and crisp crepe fabrics are required to have the characteristics of smoothness, stiffness, and smoothness, and the yarn twist should be larger.