Software Architect's Handbook

Loose coupling

Coupling is the degree to which a software module depends on another software module. Coupling between modules is a measure of how closely connected they are, and it can either be loose, sometimes described as low or weak, or it can be tight, sometimes referred to as high or strong. The degree of coupling between modules reflects the quality of their design.

Software modules that are tightly coupled are more complex, which decreases their maintainability. Tight coupling makes modifying the code more difficult because a change in a tightly coupled module will likely require changes in other modules. This introduces a higher degree of risk as there is a greater likelihood that a new defect could be introduced if a software module ...