Water activity, often abbreviated as aw, measures the availability of water in a substance for microbial growth and chemical reactions. It ranges from 0 (completely dry) to 1.0 (pure water). Foods with lower water activity are less prone to spoilage, making this measurement crucial in food science and preservation. Factors influencing water activity include temperature, humidity, and the presence of solutes like sugars and salts. By controlling aw, manufacturers can extend the shelf life of products, ensuring safety and quality. Understanding water activity helps in developing effective storage and preservation methods for various materials.