Decreasing is a method of reducing the number of stitches (usually one or two at a time) to narrow a piece of knitting.
As with increases, a variety of methods can be used, depending on the purpose they will serve. For example, decreases can slant to the left, slant to the right or be vertical. When shaping an armhole, you might want to work a left-slanting decrease on the right-hand side of the garment and a right-slanting decrease on the left-hand side of the garment, thus emphasizing the slope of the shaping. If placed one or two stitches in from the edge, the decreases become a decorative detail. This type of visible decreasing is called “full-fashioned” decreasing. Placing the decreases away from the edge also makes it easier to seam the pieces together.
Of course, the decreases do not have to be visible. A simple decrease (such as knitting two stitches together) can be placed at the edge of the knitting so that it will be invisible once the pieces are sewn together.
Most decreases are worked on the right side of the knitting, but sometimes it is necessary to decrease stitches on the wrong side (such as when the decreases are worked on every row). For this reason, we have also included decreases that can be worked on the purl side of the work.