What characterizes the "waterfall model" in software engineering?

The characteristic of the waterfall model in software engineering is defined by its linear project management approach where phases do not overlap. In the waterfall model, each phase must be completed before moving on to the next one, resembling a cascading effect where progress flows downwards through distinct stages, such as requirements gathering, design, implementation, testing, deployment, and maintenance. This sequential process ensures that each phase is fully completed and documented before the next begins, which helps in maintaining organization and clarity throughout the project.

This contrasts with other methodologies that favor iterations or overlapping phases, such as agile or iterative models, which allow for frequent testing and modifications based on feedback. The waterfall model strictly adheres to one direction through its process, which is its defining feature.