The tendency of a yam to twist or untwist spontaneously.
Note 1: Examples of effects which may be caused by twist liveliness include snarling of yarns during processing and spirality in knitted fabrics.
Note 2: The direction of twist liveliness or torque, S or Z, is that of the twist change which takes place spontaneously when an end of yam or hanging loop is allowed to rotate.
Textile Resource (http://www.textile.org.uk)