The term “yarn” is a collective term for linear textile fibers. Yarns can be made from both natural and synthetic fibers and are produced in various degrees of fineness. Different numbering systems are used to distinguish between different yarn finenesses, depending on the industry and type of yarn.
Source:
Eberle, Hannelore; Gonser, Elke; Hornberger, Marianne; et al. (2022), Fachwissen Bekleidung, 12. Auflage, Haan-Gruiten: Verlag Europa-Lehrmittel, S. 56