An abbreviation standing for the name of an element and
   consisting of the initial letter of the Latin or New Latin name, or
   sometimes of the initial letter with a following one; as, C for carbon,
   Na for sodium (Natrium), Fe for iron (Ferrum), Sn for tin (Stannum), Sb
   for antimony (Stibium), etc. See the list of names and symbols under
   Element.