Warp & weft
Also searched as: warp and weft, ends, picks, filling, selvedge, selvage
The lengthwise and crosswise yarn systems in a woven fabric.
In detail
Warp and weft are the principal yarn systems in weaving. Warp yarns run lengthwise through the loom, while weft, also called filling, crosses them. The sequence of interlacing produces the weave, and the two systems may use different yarns, colors or materials.
The science and numbers
The two systems face different mechanical demands. Warp yarns are held under tension through the whole weaving process and abraded by heddles and reed, so they are commonly given more twist and protected with size that is later removed in desizing; typical cotton twist multipliers are about 3.8 to 4.5 for warp yarns against about 3.0 to 3.6 for weft and knitting yarns. Density is counted separately as ends per unit width in the warp and picks per unit length in the weft, and the warp is set through a reed with a fixed number of dents. Interlacing makes each system bend around the other, and the resulting crimp differs between directions, one reason fabrics stretch and shrink differently lengthwise and crosswise. Denim shows the separation clearly: indigo is applied to the warp by repeated dipping and oxidation, producing ring-dyed yarn, while the weft often stays undyed.
A practical example
On a woven sample with its original selvedge, the warp direction runs along that edge. Identify both directions before comparing stretch or cutting a pattern piece. A fabric can behave differently lengthwise and crosswise even when its overall composition is unchanged.
What to distinguish
These are structural directions, not fiber names. The terminology also should not be applied casually to the loop rows and columns of ordinary weft knitting, which uses a different construction.
Origins and history
The vocabulary follows the loom. Warp names the yarns set up first and held under tension; weft, also called filling in US mill usage, names the yarn laid across them pick by pick. Because warp ends must pass through a reed, recording ends per inch is intrinsic to weaving, and the later retail thread-count figure simply adds ends and picks. Weave names describe how the two systems interlace, from the two-shed plain weave to twills needing at least three shafts.
Related terms
Sources & further reading
- CottonWorks: Weaving basics
- Textile School: Twist multiplier to TPI and TPM calculator
- Bioresources and Bioprocessing: Supramolecular encapsulation of indigo with cyclodextrins for reducing-agent-free dyeing (Devi et al., 2026)
- Heliyon: Mechanical properties of woven fabrics from 50/50 cotton-Tencel siro yarn (Afroz and Islam, 2021)
Technical references reviewed 2026-09-22. Examples are illustrative. Industry organizations and manufacturers describe their own fields; their references are not independent product endorsements. Figures are approximate and depend on the stated test conditions.