Clepsydras, also known as water clocks, were one of the earliest timekeeping devices used by ancient civilizations. While this term is commonly used to describe these early instruments, there are several synonyms that can also be used. One such term is "horologe," which is a more general term used to describe any device that measures time. Another common synonym is "timepiece," which refers to any device that is used to keep track of the hours and minutes. Other related terms include "sundial," "hourglass," and "chronometer." While these instruments have largely been replaced by modern technology, they remain an important part of human history and our understanding of the passage of time.