The central narrow bone in the front of the chest, connecting the collarbone and the top ribs.
Any of the bony or cartilaginous segments which make up the backbone, consisting in some lower vertebrates of several distinct elements which never become united, and in higher vertebrates having a short more or less cylindrical body whose ends articulate by pads of elastic or cartilaginous tissue with those of adjacent vertebrae and a bony arch that encloses the spinal cord.