Briefly contrast Agile and Waterfall project management methodologies, focusing on their core differences in approach to change and planning?

Agile and Waterfall are project management methodologies with fundamentally different approaches to change and planning. Waterfall is a sequential, linear approach where each phase of the project (requirements, design, implementation, testing, deployment) must be completed before the next phase begins. Planning is extensive and upfront; all requirements are defined at the outset, and changes are difficult and costly to implement once the project is underway. It assumes requirements are fixed and predictable. Agile, on the other hand, is an iterative and incremental approach that emphasizes flexibility and adaptability. Planning is incremental and adaptive, with short development cycles (sprints) allowing for frequent feedback and adjustments. Agile methodologies embrace change; requirements can evolve throughout the project as new information becomes available or customer needs shift. Agile is suited for projects where requirements are likely to change or are not fully understood at the beginning, while Waterfall is best suited for projects with well-defined and stable requirements.