Bias in fabric is an imaginary diagonal “line” intersecting the lengthwise and crosswise grain at a 45° angle.
Wovens and knits stretch on the bias. This is known as mechanical stretch.
Cut on the bias when you need stretch in woven fabrics.
Woven fabrics do not fray on the bias.
Bias cut dresses were popular in the late 1920s and 1930s. Madeline Vionnet
was famous for her body hugging gowns that were cut on the bias.