Second

Second, measurement of time and angles in the metric system. In time, 60 seconds make up 1 minute; 60 minutes make up 1 hour. In measuring angles, 60 seconds make up 1 minute and 60 minutes make 1 degree. According to the standard established by use of an atomic clock, a second is defined as 9,192,631,770 times the vibration of radiation from a cesium atom.

See also: Metric system.