A rope lay is the length along the rope that a strand makes one complete spiral around the rope core.  This is a measurement frequently used.  This is a measurement frequently used in wire rope inspection.  Standards and regulations require removal when a certain number of broken wires per rope lay are found.

Strands that are wound to the right are right hand lays.  Strands that are wound to the left are left hand lays.  Wires that are wound in the opposite direction of the strand is a regular lay.  Wires that are wound in the same direction as the strand is a lang lay.