valency

Etymology

From Late Latin valentia and Latin valentia (“bodily strength; health; vigour”) + English -y (suffix forming abstract nouns denoting a condition, quality, or state). Valentia is derived from valēns (“healthy, strong, vigorous”) + -ia (suffix forming feminine abstract nouns); while valēns is the present active participle of valeō (“to be healthy, sound, or well; to be strong; to have influence or power, etc.”), ultimately from Proto-Indo-European *h₂welh₁- (“to rule; powerful, strong”). Sense 1 (“combining capacity of an atom”) and sense 3 (“number of arguments a verb can have”) are possibly from valence + -y.

noun

1. (countable, chemistry) 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.”)
   1. (uncountable, by extension) 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.
      vaccine valency
      Some etymons appear to have greater valency than others when it comes to the formation of portmanteau words. 2018, James Lambert, “A Multitude of ‘Lishes’: The Nomenclature of Hybridity”, in English World-Wide, page 10
      The rationale behind GSK's buy is that bigger is better, in terms of vaccine valency. It has been shown that including more disease-causing serotypes decreases the incidence of invasive pneumococcal disease. To this end, Pfizer and Merck last year got the nod for 20-valent and 15-valent vaccines respectively. Affinivax's AFX3772, meanwhile, is a 24-valent jab. 2022-05-31, Madeleine Armstrong, “GSK goes back to its vaccine bread and butter”, in Evaluate Vantage, retrieved 2023-05-09
2. (countable, graph theory) The number of edges connected to a vertex in a graph.
3. (countable, linguistics) Alternative form of valence (“the number of arguments that a verb can have, including its subject, ranging from zero to three or, less commonly, four”)
4. (uncountable) Importance, significance.