Nonmetal :: Nonmetal (n.) Any one of the set of elements which, as contrasted with the metals, possess, produce, or receive, acid rather than basic properties; a metalloid; as, oxygen, sulphur, and chlorine are nonmetals..
Nonmetallic :: Nonmetallic (a.) Resembling, or possessing the properties of, a nonmetal or metalloid; as, sulphur is a nonmetallic element..