Waterfall (or traditional/predictive) is a [[project management]] approach that focuses first and foremost on developing a project plan and then executing the plan. The plan drives the project. Waterfall is best when the requirements are well known, execution is well tested and outcomes are predictable. Waterfall involves a step-wise process from requirements -> design -> development -> testing -> deployment. Most software projects take 6-9 months. If the project outcomes are not highly predictable success criteria may change significantly by the time the project is deployed. Further, the investment is significant before meaningful user feedback can be collected. Contrast with [[Agile]]. Many organizations use a hybrid project management approach that combines Agile and Waterfall practices.