Modularity is a frequently used term in information technology and computer science. Modularity refers to the concept of making multiple modules first and then linking and combining them to form a complete system. Modularity enables re-usability and minimizes duplication.

In addition to re-usability, modularity also makes it easier to fix problems as bugs can be traced to specific system modules, thus limiting the scope of detailed error searching. Modular programming is an extensively used concept based on modularity. Modularity is also a feature of object oriented programming.

Modularity definition
Modularity is the degree to which a system’s components are made up of relatively independent components or parts which can be combined.

The figure shows modules of a puzzle which can form different shapes when they are placed at different places. The modules can be moved freely without affecting the functionality of other modules but it changes the system’s shape(functionality).