Linen is a material made from the fibers of the flax plant. When these fibers are twisted together (spun), it is called yarn. It is strong, durable, and resists rotting in damp climates. It is one of the few textiles that has a greater breaking strength wet than dry. It has a long "staple" (individual strand length) relative to cotton and other natural fibers. The fiber in its un-spun state is called flax. After it is spun into yarn it becomes linen.
The standard measure of bulk linen yarn is the lea. A yarn having a size of 1 lea will give 300 yards per pound. The fine yarns used in handkerchiefs, etc. might be 40 lea, and give 40x300 = 12000 yards per pound.
Up until around 1950s the finest linen yarn was made in Scotland, Ireland (Irish Linen), and Belgium. The climates of these locations were ideal for natural processing methods called "retting". As years went by many of the finest factories in those areas closed, and most linen is currently made in China.
The decrease in the use of linen may be attributed to the increasing quality of synthetic fibers, and a decreasing appreciation of buyers for very high quality yarn and fabric that wrinkles easily and requires high-temperature ironing while damp. Very little top-quality linen is produced now, and most is used in low volume applications like hand weaving and as an art material.
Linen will withstand washing in hot water and scrubbing, and can be bleached by spreading it in the sun to dry. These properties led to its use from the early Middle Ages for underwear, shirts, chemises, and other clothing worn next to the body (collectively called "body linen"), and also for sheets and pillowcases, napkins, and tablecloths. Although these are now often made of cotton or synthetic fibers, they are still called "linens," "bed linens," and "table linens."
Linen is also used for cloth, canvases, sails, tents, and paper. Due to its strength, in the Middle Ages, linen was used for shields and gambeson.
Linen is available in different quailities varying from almost silk-like to sack-linen. Linen is usually white to ivory, may be washed at 95°C, and should be ironed when damp. A characteristic often associated with linen yarn is the presence of "slubs", or small knots that occur randomly along its length. However, these are actually defects associated with low quality. The finest linen has a very consistent diameter with no slubs. When being washed for the first time, linen shrinks significantly.