Ply (layer)

A ply is a layer of material which has been combined with other layers in order to provide strength. The number of layers is indicated by prefixing a number, for example 4-ply, indicating material composed of 4 layers.

Etymology
The word "ply" derives from the French verb plier, "to fold", from the Latin verb plico, from the ancient Greek verb πλέκω.

Examples

 * Yarn, where plying is a spinning technique to combine several fibres.
 * Vehicle tires
 * Plywood
 * Toilet paper