Anhydrous refers to a substance that does not contain water. This term is often used in chemistry to describe compounds that have had all water removed, making them dry. For example, anhydrous sodium sulfate is a common drying agent in laboratories, as it can absorb moisture from the air. In various industries, anhydrous materials are important for specific applications. For instance, anhydrous ammonia is used as a fertilizer in agriculture because it provides nitrogen without the added weight of water. Understanding the properties of anhydrous substances helps in their effective use in different fields.