- In <em>chem.</em>, noting an atom the equivalence of which is four, or an element one atom of which is equivalent, in combining power, to four atoms of hydrogen; tetradic; tetratomic.
- A quadrivalent atom or element.
- Having a valence of four; capable of combining with, being replaced by, or compared with, four monad atoms; tetravalent; -- said of certain atoms and radicals.
- Having a <xref>valence</xref> of <xref>four</xref>.
- Any quadrivalent chromosome.