A water clock, also known as a clepsydra, is a device that measures time using the flow of water. There are several other synonyms for water clock, including hydraulic clock, hydrochronometer, and water timepiece. These terms all refer to the same type of device, which was used by ancient civilizations to tell time based on the level of water in a container. In addition to its practical use, water clocks were also used as decorative items and were often found in courtyards and gardens. While modern technology has rendered them mostly obsolete, water clocks remain an interesting piece of historical and technological curiosity.