rach(i)-

The spine.

Modern Latin rachis, from Greek rhakhis, spine.

A rachis can be a stem of a plant bearing flower stalks at short intervals, or the spine of an animal, or the cord from which it develops, or the shaft of a feather, especially the part bearing the barbs; rachilla, a diminutive of rachis, is a spikelet that bears the florets, as in grasses and sedges; rachitis is an older medical term for rickets; rachischisis is another term for spina bifida.