Shelf life refers to the length of time that a product, especially food or medicine, remains safe and effective to use. It is determined by factors such as the type of product, storage conditions, and packaging. After the shelf life has expired, the product may not be safe to consume or may lose its intended effectiveness. Manufacturers often indicate shelf life on packaging using "best by," "use by," or "expiration" dates. These labels help consumers understand when a product is at its best quality. Proper storage, such as keeping items in a cool, dry place, can help extend the shelf life of products like canned goods or medications.