Many different types of yarn can be manufactured for different end uses. The two most common types of yarn are staple spun yarn and continuous filament yarn. A staple spun yarn, also known as staple yarn or spun yarn, is made from staple fibres, i.e. fibres of limited and relatively short length. Staple fibres may be divided into two categories, namely, short and long staples. Short staple refers to fibres of less than about 2 inches long, whereas long staple describes those longer than about 2 inches. Natural fibres such as cotton and wool are typical examples of short staple and long staple respectively.

Manufactured filaments can be cut or stretch-broken into short lengths to become either short staple or long staple fibres. A continuous filament yarn is normally produced in a chemical plant. It is a yarn composed of one or more filaments that run essentially the whole length of the yarn. If there is only one filament in the yarn, then it is called a mono-filament yarn.

A multi-filament yarn consists of many filaments. Most yarns are used in singles or plied forms. A singles yarn is the simplest continuous strand of textile material, either as a single staple spun yarn, a mono or multi-filament yarn, or a composite yarn consisting of staple fibres and continuous filaments. A plied yarn is formed by twisting together two or more singles yarns. A cable and cord yarn consists of many plied yarns (or plied and single yarns) twisted together. A graphical depiction of the various forms of yarn structures is given in Figure

Yarn count

Yarns are manufactured in different sizes for different purposes. They can be quite thick, or they can be very thin. Since by their very nature textile yarns are soft and squashy, the ‘thickness’ of a yarn can not be easily measured by yarn diameter. But textile yarns are often sold on a weight basis, so it is natural to express the size of a yarn in terms of its weight or mass. The two basic ways of doing this are by indicating either how much a given length of yarn weighs (the direct system) or what the length of yarn will be in a given weight (the indirect system). These two broad yarn count systems are expressed below:

Because a textile yarn is usually a very slender assembly of tiny fibres, it is conceivable that the weight of a yarn in a given length will be very small while the length of a yarn in a given weight will be quite large. Consequently, the yarn count figures would get either incredibly small (direct system) or large (indirect system) unless special units are used. Over the years, many different units have been used in different sectors of the textile industry. The commonly used ones are described in the following sections.