In chemistry, polyvalence or multivalence refers to species

Chemical species

Chemical species are atoms, molecules, molecular fragments, ions, etc., being subjected to a chemical process or to a measurement. Generally, a chemical species can be defined as an ensemble of chemically identical molecular entities that can explore the same set of molecular energy levels on a...

 that are not restricted to a distinct number of valence

Valence (chemistry)

In chemistry, valence, also known as valency or valence number, is a measure of the number of bonds formed by an atom of a given element. "Valence" can be defined as the number of valence bonds...

 bonds

Chemical bond

A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms. The bond is caused by the electromagnetic force attraction between opposite charges, either between electrons and nuclei, or as the result of a dipole attraction...

. (Species with only one valence are univalent (monovalent)). For example, the Cs⁺ cation is a univalent or monovalent cation, whereas the Ca²⁺ cation is a divalent or polyvalent or multivalent cation and the Fe³⁺ cation is a trivalent or polyvalent or multivalent cation. As a result, examples of polyvalent cations include the Ca²⁺ cation and the Fe³⁺ cation.

Specific uses may refer to:

• Polysemy
  Polysemy
  Polysemy is the capacity for a sign or signs to have multiple meanings , i.e., a large semantic field.Charles Fillmore and Beryl Atkins’ definition stipulates three elements: the various senses of a polysemous word have a central origin, the links between these senses form a network, and ...
  
  
• Polyvalent vaccine, a vaccine that can vaccinate a person against more than one strain of a disease
• Antivenoms are classified as polyvalent when they are effective against a range of species, or several different species at the same time