adjuvancy
/ˈadʒʊv(ə)nsi/Now chiefly Medicine
noun
The capacity or effect of assisting something or someone; assistance, aid, help. In later use chiefly with reference to the action of adjuvant therapies or agents.
Origin
Late 17th century; earliest use found in John Brown (c1610–1679), Church of Scotland minister. From adjuvant: see -ancy.