The primary functions of a leaf include photosynthesis, gas exchange, and transpiration. During photosynthesis, leaves capture sunlight and convert carbon dioxide and water into glucose and oxygen. The process of gas exchange occurs through small openings called stomata, allowing carbon dioxide to enter and oxygen, along with water vapor, to exit. Transpiration, the loss of water vapor from plant surfaces, helps to regulate temperature and maintain nutrient flow. Overall, leaves play a vital role in a plant's ability to thrive and adapt to its environment.