The number of specialty stitches (ie other than straight-stitch and zig-zag) that are available on a sewing machine. Some may be decorative like scallops, curlicues and arrowheads; other stitches are functional, such as treble-seaming, overcasting, blind-hemming or stretch stitches. Stitches that form buttonholes are also commonly built-in.
Some older sewing machines (usually pre-1990’s) can produce decorative stitches with the use of cams or discs. The specially-shaped cams or discs are inserted into the machine at a point where they align with the inner gears, and they cause the needle and feed dogs to move in such a way that the decorative stitch is produced when the sewer steps on the foot pedal.
Newer, computerized sewing machines tend to have many more built-in stitches than their older mechanical counterparts.