Hourglasses are ancient time measuring devices that have been used for centuries. These beautiful and intriguing devices come in a variety of sizes and shapes, but they all share one thing in common: the sand that trickles through their narrow middles to measure time. One of the most common synonyms for hourglasses is sand timers. This term accurately describes the primary function of an hourglass, which is to measure time using sand as a visual cue. Another synonym for hourglasses is sand clocks. This term has a historical connotation since the earliest versions of hourglasses were made of blown glass and filled with sand. Finally, the word "chronometer" can also be used to describe an hourglass, although this term is typically reserved for more precise timekeeping devices that use mechanical or electronic mechanisms.