Association (aka Relation, Morphism), represents two or more things that are in some way connected. It is used in UML#1.3.6.1.4.1.33097.3.50 as the basis of the other relationship categorization and also essentially a synonym for a Nodes#1.3.6.1.4.1.33097.1.0.12.0 in GraphTheory#1.3.6.1.4.1.33097.1.0.14 .
https://en.wikipedia.org/wiki/Association_(object-oriented_programming)
https://www.geeksforgeeks.org/system-design/association-class-relationship/
https://en.wikipedia.org/wiki/Category_theory