Full name: second
Plural form: seconds
Alternate spelling: sec
Category type: time
Scale factor: 1
The SI base unit for time is the second.
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The second (symbol s) is a unit for time, and one of seven SI base units. It is defined as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom at zero kelvins.