Why do teapots have a hole in the lid?

A small air hole in the lid is often created to stop the spout from dripping and splashing when tea is poured. Teapots usually have an opening with a lid at their top, where the dry tea and hot water are added, a handle for holding by hand and a spout through which the tea is served. Some teapots have a strainer built-in on the inner edge of the spout. In modern times, a thermally insulating cover called a tea cosy may be used to enhance the steeping process or to prevent the contents of the teapot from cooling too rapidly.