A lid is a cover that fits over the top of a container, such as a pot, jar, or box. It serves to protect the contents from dust, spills, and contamination while also helping to retain heat or freshness. Lids can be made from various materials, including plastic, metal, and glass, and they come in different shapes and sizes to match the containers they cover. Lids can also be designed with specific features, such as airtight seals or easy-open mechanisms. In cooking, a lid can help food cook more evenly by trapping steam and heat. Common examples of lids include those found on saucepans, storage jars, and bottles.