Prohibitions by commandment [are] —- secondary [arayos] by Rabbinical decree. Prohibitions because of sanctity [are] —- a widow to a Kohen Gadol; a divorcee or a chalutzah to an ordinary Kohen; a mamzeress or Nesinite to a Yisrael; and the daughter of a Yisrael to a Nesinite or mamzer.