twisting of fibres in the direction of the helix around the axis of the yarn. The t. strengthens the yarn; its number - given per 1 m - is dependent on the fineness of the yarn, the length and fineness of the fibre, and the purpose the yarn will serve. We distinguish between left-hand [[101143|S t.]] (indicated by the letter "S"), and right-hand [[101544|Z t.]] (indicated by the letter "Z").