Clock

A clock (from the Latin cloca, "bell") is an instrument for measuring time. A clock is usually a physical instrument; an especially accurate one is called a chronometer. The clock in its modern form (24 hour clock) has been in use since at least the 14th century. Clock can refer to an abstract system of time measurement (see calendar for other measurements). Modern clocks define constant units of time: an hour is always sixty minutes, of sixty seconds each.

See also

• chronometer
• radio clock
• timer
• Iron Ring Clock
• Allan variance
• biological clocks
• clock face
• Cox's timepiece
• Clock of the Long Now
• Clock signal (digital circuits)
• clock tower
• clockmaker
• Horology
• Intellectual history of time
• Metrology
• Star clock
• Timeline of time measurement technology
• Time standard
• watchmaker
• Colgate Clock, the world's largest clock