valency

noun4

1. •
   The capacity of something to combine with other things, as for example the capability of a vaccine as measured by the number of pathogen serotypes that it can counteract.

   • Some etymons appear to have greater valency than others when it comes to the formation of portmanteau words. — 2018
2. •
   Alternative form of valence (“the combining capacity of an atom, functional group, or radical determined by the number of atoms of hydrogen with which it will unite, or the number of electrons that it will gain, lose, or share when it combines with other atoms, etc.”).
3. •
   Importance, significance.
4. •
   The number of edges connected to a vertex in a graph.