yarn, fibers or filaments formed into a continuous strand for use in weaving textiles or for the manufacture of thread. A staple fiber, such as cotton, linen, or wool, is made into yarn by carding, combing (for fine, long staples only), drawing out into roving, then spinning. Continuous filaments, such as silk, rayon, and nylon, may be formed directly into yarn or may be cut into short lengths and prepared like staple fibers. Yarns are twisted to give them strength and smoothness; a clockwise twist is known as the Z twist and a counterclockwise twist is known as the S twist. Two or more strands twisted together form ply yarns. In slub yarns areas are left untwisted to vary the diameter for ornamental effects. Complex yarns, such as bouclé and ratiné, are made by twisting together yarns of different tensions or diameters. The relation between the weight of the raw fiber of staple yarns and the yarn length is expressed by the yarn number; the finer the yarn, the higher the number. In filament yarns the yarn number, expressed in deniers, increases with the coarseness of the yarn.

Continuous strand of fibres grouped or twisted together and used to construct textile fabrics. Yarns are made from both natural and synthetic fibres, in filament or staple form. Filament is very long fibre, including the natural fibre silk and the synthetic fibres. Most fibres that occur in nature are fairly short, or staple, and synthetic fibres may be cut into short, uniform lengths to form staple. Spinning is the process of drawing out and twisting a mass of cleaned, prepared fibres. Filament yarns generally require less twist than do staple yarns. More twist produces stronger yarn; low twist produces softer, shinier yarn. Two or more single strands may be twisted together to form ply yarn. Knitting yarns have less twist than weaving yarns. Thread, used for sewing, is a tightly twisted ply yarn.

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Wool yarn made of long-staple fibres that have been combed to remove unwanted short fibres and make them lie parallel. In the spinning operation, which gives the necessary twist to hold the fibres together, worsted yarns are more tightly twisted than are the bulkier woolen yarns. The soft, heavy yarn is strong and durable and is often used for sweaters. Worsteds are also used for fine dress fabrics and suit material.

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