Polyvalent element is a molecule which having more than one valence, for example oxygen is a divalent in H2O, nitrogen is a trivalent in NH3, carbon is a tetravalent in methane (CH4).
Generalic, Eni. "Polyvalent element." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
Glossary
Periodic Table