What is one key characteristic of the Waterfall model?

The Waterfall model is characterized by a structured and sequential approach to software development, where each phase must be completed before the next one begins. This one-way flow of activity is fundamental to the Waterfall methodology. In this model, requirements are gathered at the beginning of the project, and following that, the design, implementation, verification, and maintenance phases occur in a linear fashion.

Each phase produces deliverables that are handed off to the following phase. Because of this sequential nature, the model does not accommodate revisiting earlier phases easily, which reinforces the concept of a one-way flow of activities. Overall, the Waterfall model's rigid structure is aimed at creating clarity and ensuring that every aspect of development is documented and completed thoroughly before moving on to the next stage.