Cohesion in software engineering refers to the degree to which the elements within a module or component are related and work together to achieve a common goal or functionality.

In simpler terms, it is the measure of how well the different parts of a software system are connected and function as a unit. High cohesion is a desirable quality in software development as it leads to modules that are focused, well-defined, and easier to maintain.

When a module has high cohesion, it means that the elements within it are closely related and work together to perform a specific task or function.

This makes the module more self-contained and independent, reducing the chances of bugs and errors. On the other hand, low cohesion indicates that the elements within a module are loosely related and may not have a clear purpose or function.

This can lead to modules that are difficult to understand, modify, and test, making the software system as a whole more complex and error-prone. There are different types of cohesion, including functional cohesion, sequential cohesion, communicational cohesion, and temporal cohesion, each describing a different aspect of how well the elements within a module are connected. In summary, cohesion is an important concept in software engineering that helps developers create modular, maintainable, and reliable software systems.

By striving for high cohesion in their code, developers can ensure that their software is well-structured, easier to understand, and less prone to errors.