Yarn Terminology (a) Yarn number: You may have seen certain numbers , , , etc., on the labels of thread reels. If you observe carefully and compare the fineness of the thread you will realise that thread reel with a higher number is finer. There is a fixed relationship between the weight of the fibre and the length of yarn drawn from it. This is designated as yarn number which becomes the indication of the fineness of the yarn.
(b) Yarn twist: As fibres are transformed into yarn, twist is added to hold the fibres together and is indicated as t.p.i. (twist per inch). Loosely twisted yarns are softer and more lustrous, whereas tightly twisted yarns may show as ridges such as in denim material of jeans. (c) Yarn and thread: Yarn and thread are basically similar.
Yarn is the term usually used in the manufacturing of a fabric, whereas, thread indicates a product used to join pieces of fabrics together.