## Wikipedia - Anno (it) Wikipedia - ثانية (ar) second, $$\text{s}$$

https://doi.org/10.1351/goldbook.S05513
The second, symbol $$\text{s}$$, is the SI unit of time. It is defined by taking the fixed numerical value of the caesium frequency $$\Delta\nu_\text{Cs}$$, the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be $$9\ 192\ 631\ 770$$ when expressed in the unit Hz, which is equal to $$\text{s}^{-1}$$.
Source:
BIPM, The International System of Units, SI Brochure, 9th ed. (2019), p. 130 [Terms] [Book]