A second is the SI base unit of time. It's called a second because it's the second division of an hour, the first being minutes. One second is 1/60 of a minute, and 1/3600 of an hour.
Base or Derived:
The second is a base unit. One second is the amount of time that passes for the frequency of the radiation emmitted by cesium-133 to equal to 9,192,631,770 hertz.
Second:
Define :
A second is the SI base unit of time. It's called a second because it's the second division of an hour, the first being minutes. One second is 1/60 of a minute, and 1/3600 of an hour.Base or Derived:
The second is a base unit. One second is the amount of time that passes for the frequency of the radiation emmitted by cesium-133 to equal to 9,192,631,770 hertz.Source:
http://www.unc.edu/~rowlett/units/dictS.htmlhttp://wwp.greenwichmeantime.com/info/si.htm