The term "ply" refers to a single layer or strand in fabric, paper, or other materials. In textiles, ply means the number of yarns twisted together to form a thread, and the higher the ply, the stronger and more durable the material will be. For example, a two-ply towel is made from two layers of cotton woven together, while a four-ply yarn is composed of four individual strands twisted together. In paper, "ply" refers to the number of sheets that are bonded together in the manufacturing process. The higher the ply, the stronger and more durable the paper will be.