A question was sent to me asking the difference between stretch woven fabrics and knit fabrics. There are 3 main types of fabric fabrications. Woven, Knit and Film. The main difference between woven vs knit fabrics is how they are constructed.
Woven fabrics are created using several warps, or longitudinal yarns, this runs the length of the fabric and in sewing we refer to it as the grain line, and wefts, or latitudinal yarns, referred to cross grain. Woven fabrics are formed on a loom. Selvages are formed on each lengthwise sides by the weft yarns wrapping the warp yarns. There is no stretch lengthwise or crosswise and the fabric will give a little on the bias (45 degree angle) and in loosely woven fabrics and twill weaves (like your denim jeans).
Woven fabrics become stretch woven fabrics when spandex is an added yarn., either in the weft or warp or both. Spandex is various elastic textile fibers made chiefly of polyurethane. Spandex is a generic term, it is not a trademark name as a number of the names of other fibers are. Brand names for spandex include Lycra (made by Koch subsidiary Invista, previously part of DuPont), Elaspan (also Invista), Acepora (Taekwang Group), Creora (Hyosung), INVIYA (Indorama Corporation), ROICA and Dorlastan (Asahi Kasei), Linel (Fillattice), and ESPA (Toyobo). There is stretch found in stretch woven fabrics, sometimes found lengthwise, sometimes found crosswise, sometime both, depending on the direction of the spandex in the weave. As spandex formulas improve, stretch recovery has improved.
Knitted fabrics are looped yarns, involving interloping or interlacing a single yarn or thread. In the industry many of the knitted fabrics are formed on a circular knitting machine and the knit is later cut along the grain line and sealed. Often the edge is mistaken for the selvage edge.
Knitted fabrics that have spandex yarns added become 2 way stretch knit fabrics. They stretch width wise and length wise.
Film fabrication is found in plastic sheeting, felt …
Sewing patterns are sized specifically for the fabric fabrications. The wearing ease changes with each type of fabrication due to the amount of stretch.