concept
Cohesion
The degree to which everything inside one component belongs together and changes for the same reason.
High cohesion means that the things inside a module change together, are deployed together, and are owned by the same people. Low cohesion means a module is a bag of unrelated things that happen to sit in the same folder — a "utils" service, a "common" library, a shared database that five teams write to.
Cohesion and coupling are two views of the same choice: where the boundary goes. Move a boundary to reduce coupling and you usually reduce cohesion somewhere else. The goal is not to maximise one, it is to put boundaries where the change patterns actually are.