Yarn Twist , means the direction of twisting the fibre during spinning proccess. It isveryimportant in the knitted fabric. In general practise we use “Z ” Type Twist yarn, But we can use the “S ” Type twist also .

Twist is the spiral arrangement of the fibres around the axis of the yarn. The twist binds the fibres together and also contributes to the strength of the yarn. The amount of twist inserted in a yarn defines the appearance and the strength of the yarn. The number of twists is referred to as turns per inch. 

Twist direction:  
The direction of the twist at each stage of manufacture is indicated by the use of letters S or Z in accordance with the following convention:

A single yarn has S twist if, when it is held in the vertical position, the fibres inclined to the axis of the yarn conform in the direction of the slope to the central portion of the letter S. Similarly the yarn has Z twist if the fibres inclined to the axis of yarn conform in the direction of slope to the central portion of the letter Z.