Fiber is a soft and slender substance, with an aspect ratio of at least 10: 1 and a cross-sectional area of less than 0.05mm2 For textile fibers, the aspect ratio is generally greater than 1000: 1.

Chemical fiber products are cut into lengths of several centimeters to more than ten centimeters, and the fibers of this length are called short fibers. According to the different cut lengths, short fibers can be divided into cotton type, wool type and medium-long type.

The length of cotton fiber is 30 ~ 40 mm, the linear density is about 1.67dtex, and the fiber is fine, similar to cotton. The length of wool fiber is 70 ~ 150 mm, and the linear density is 3.3~7.7dtex, which is thick and similar to wool. The length of intermediate fiber is 51~ 65 mm, and the linear density is 2.2～3.3 dtex, which is between cotton type and wool type.