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The second (s) is the unit of time (t). The concept is based on the Sumerian hexagesimal numeral system (third millennium BC), but the name is derived from the Latin expressing pars minuta secunda, meaning "second diminished part". This expression goes back to the Persian scholar Abu Rayhan al-Biruni (973 – 1048).

The second is defined as 1/9192631770 of the frequency of the 133Cs atomic clock.

Related units:

Last modified:04 March 2024 3.05 p.m.
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