The Collaborative International Dictionary of English v.0.48:

Basis \Ba"sis\ (b[=a]"s[i^]s), n.; pl. Bases (b[=a]"s[=e]z).
   [L. basis, Gr. ba`sis. See Base, n.]
   1. The foundation of anything; that on which a thing rests.
      --Dryden.
      [1913 Webster]

   2. The pedestal of a column, pillar, or statue. [Obs.]
      [1913 Webster]

            If no basis bear my rising name.      --Pope.
      [1913 Webster]

   3. The groundwork; the first or fundamental principle; that
      which supports.
      [1913 Webster]

            The basis of public credit is good faith. --A.
                                                  Hamilton.
      [1913 Webster]

   4. The principal component part of a thing.
      [1913 Webster]