A subdial, also known as a subsidiary dial, is a smaller dial located on the main dial of a watch. It serves to display additional information beyond the basic timekeeping function. Subdials are commonly found on chronograph watches, where they are used to measure elapsed time, often displaying seconds, minutes, and hours separately. They can also indicate other functions such as a second time zone, power reserve, or moon phase. The design of subdials can vary, typically appearing in round or square shapes, and their number can range from one to four, depending on the watch's complexity and intended functions. Subdials enhance the functionality and aesthetic appeal of a watch, providing users with more detailed information at a glance.