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.
