A weaving term for yarns in woven fabrics and carpets which run in the machine direction (or lengthwise). Warp yarns are usually delivered to a weaving loom from a beam mounted behind the loom. Woven carpets usually have three sets of warp yarns, which may be wound on three loom beams. These include stuffer warp for lengthwise strength and stiffness, pile warp which forms the carpet surface tufts, and chain warp which interlaces with fill yarn to lock the structure together.