According to the Textile Institute, yarn may be defined as such a product of substantial length, relatively small cross, and section, maintaining fibers or filaments, having with or without twist.
Classification of Yarn:
Yarn mainly classified into two types. They are:
  1. Spun Yarn.
  2. Filament Yarn.
Spun Yarn: The type of yarn in which the fibers are twisted together. The spun yarn can be also classified into three types. They are:
            a. Single Yarn: In which the fibers are spun/twisted together or containing long strand of fibers.
            b. Complex yarn: A core spun yarn containing a core or long filament. Staple fibers are spun/twisted around the filament or core is called core yarn/complex/spun tex yarn.
            c. Folded/Plied yarn: Two or more single yarn is twisted together. Folded yarn can be also classified into two types. They are:
                        i. Cabled Yarn: Two or more plied yarn is twisted together.
                        ii. Multi-folded yarn: Tow or more cabled yarns are twisted together.
Filament Yarn: Filament yarn is made of one or more continuous strand.