What are the lengthwise yarns in a woven fabric called?

In woven fabric, the lengthwise yarns are referred to as warp yarns. These yarns run parallel to the selvage (the finished edge of the fabric) and provide the primary structure and strength to the weave. When creating fabric on a loom, the warp yarns are set up first and remain in place while the weft yarns, which run across the width of the fabric, are woven in and out of them. Understanding this distinction between warp and weft is essential for upholstery and fabric cleaning technicians, as it helps in recognizing the fabric composition and how the fabric behaves during cleaning processes.