Stitches are blocks that are used to build knit structures. Hand knitting stitches include—for example—knit, purl, rib, single jersey, stockinette stitch, and seed stitch. Often the fabric created by repeating a stitch shares the name of the stitch.
There is neither an exhaustive vocabulary of known stitches or a unique way to divide any given knit object into stitches. When describing machine knitting, we prefer to use operations, which are well-defined, non-redundant, and unique (up to unravelling).
Many—but not all—hand-knitting stitches can be converted into machine operations.