Polyester yarn refers to the yarn spun from polyester. Polyester is a kind of fiber made by spinning a kind of polymer. At present, it refers to the fiber produced by using ethylene phthalate as raw material. The English name is "polyethylene terephthalate", abbreviated as "PET" fiber. It is commonly known as polyester in China. The so-called "yarn" is actually a general term for "yarn" and "line". It is defined in the material science of clothing as follows: "Yarn" is to arrange many short fibers or filaments in an approximately parallel state and along the axial direction. Rotating twisting to form an elongated object with a certain strength and linear density; and "line" is a strand formed by twisting two or more single yarns. Yarn is cotton, wool, hemp, chemical fiber, etc., which is made of finely twisted and twisted fibers (usually used as raw materials for woven fabrics), and then made of cotton, hemp, silk, wool and other fine materials. Fine, called the thread.