A "4D model" refers to a representation that includes four dimensions: three spatial dimensions (length, width, height) and one temporal dimension (time). This concept is often used in fields like physics, computer graphics, and architecture to visualize how objects change or move over time. In computer graphics, a 4D model can help simulate complex animations or visualize data that evolves, such as weather patterns or traffic flow. By incorporating time, these models provide a more dynamic understanding of how systems behave, making them valuable for analysis and decision-making in various industries, including engineering and urban planning.