Warp & Weft:
The lengthwise or longitudinal yarn of fabric is termed as the warp yarn, while the width-wise or transverse yarn is called the weft or fill yarn.
Identification of warp and weft:
• The selvedge always runs in the lengthwise (warp) direction of all fabrics.
• Most fabrics have lower elongation in the warp direction.
• The warp yarns lie straighter and are more parallel in the fabric because of loom tension.
• Fancy or special function yarns are usually in the filling direction.
• Warp yarns tend to be smaller, are more uniform in structure and appearance and have a higher twist.
• Fabric crimp is usually greater for weft yarns.
• Fabric characteristics may differentiate between the warp and weft directions. For example, denim has a warp face and satin has warp floats and poplin has a weft rib.