Abscisic acid (ABA) is a phytohormone that plays a critical role in plant growth, development, and stress responses. It is involved in regulating various processes such as seed dormancy and germination, stomatal closure, fruit ripening, and response to environmental stresses such as drought, salt, and cold. ABA acts as a signaling molecule that helps plants adapt to changes in their environment by controlling gene expression and physiological responses. Research on ABA has implications for improving crop yields, enhancing stress tolerance, and understanding plant biology at the molecular level.