\Tet"ra-\ [Gr. te`tra-, from te`sares, te`ttares, four.
See {Four}.]
1. A combining form or prefix signifying four, as in
   tetrabasic, tetrapetalous.
2. (Chem.) A combining form (also used adjectively) denoting
   four proportional or combining parts of the substance or
   ingredient denoted by the term to which it is prefixed, as
   in tetra-chloride, tetroxide.