Seasonal variation refers to changes in a particular phenomenon or factor that occur over the course of a year. This can include changes in climate, weather patterns, biological processes, human behavior, and more. Seasonal variation is often driven by factors such as the tilt of the Earth's axis, the position of the Earth in relation to the sun, and other natural cycles. Researchers studying seasonal variation may analyze data trends, conduct experiments, and develop models to understand and predict how different factors fluctuate throughout the year. This research can have important implications for fields such as agriculture, public health, environmental science, and economics.