cohesion

Cohesion refers to the degree to which the elements inside a module belong together.
Cohesion is a type of measurement and is usually described as “high cohesion” or “low cohesion”. 
* Modules with high cohesion is preferable, because high cohesion is associated with robustness, reliability, reusability, and understandability. 
* In contrast, low cohesion is hard to maintain, test, reuse, or even understand.