S-Twist Yarn

What does S-Twist Yarn mean?

A left handed twisted yarn.

Also see Z-Twist.

Heddels explains S-Twist Yarn

S-twist yarn is a yarn spun counter-clockwise and is normally used to create right-handed twill,  while Z-twist yarn is used for left-handed twill. By opposing the direction of the yarn and the direction of the twill, the finished material is softer than fabric created with a corresponding yarn and twill weave.

Additional Resources

Here is an illustration of S-Twist Yarn:

Heddels Definition - S-Twist