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The second (symbol: s) is a unit of time, historically defined as 1 ⁄ 86400 of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds each (24 × 60 × 60 = 86400). The current and formal definition in the International System of Units (SI) is more precise:
One trillionth of a second. nanosecond: 10 −9 s: One billionth of a second. Time for molecules to fluoresce. shake: 10 −8 s: 10 nanoseconds, also a casual term for a short period of time. microsecond: 10 −6 s: One millionth of a second. Symbol is μs millisecond: 10 −3 s: One thousandth of a second. Shortest time unit used on ...
The SI comprises a coherent system of units of measurement starting with seven base units, which are the second (symbol s, the unit of time), metre (m, length), kilogram (kg, mass), ampere (A, electric current), kelvin (K, thermodynamic temperature), mole (mol, amount of substance), and candela (cd, luminous intensity). The system can ...
1.67 minutes (or 1 minute 40 seconds) 10 3: kilosecond: 1 000: 16.7 minutes (or 16 minutes and 40 seconds) 10 6: megasecond: 1 000 000: 11.6 days (or 11 days, 13 hours, 46 minutes and 40 seconds) 10 9: gigasecond: 1 000 000 000: 31.7 years (or 31 years, 252 days, 1 hour, 46 minutes, 40 seconds, assuming that there are 7 leap years in the interval)
A mathematical symbol is a figure or a combination of figures that is used to represent a mathematical object, an action on mathematical objects, a relation between mathematical objects, or for structuring the other symbols that occur in a formula. As formulas are entirely constituted with symbols of various types, many symbols are needed for ...
"The kelvin, symbol K, is the SI unit of thermodynamic temperature. It is defined by taking the fixed numerical value of the Boltzmann constant k to be 1.380 649 × 10 −23 when expressed in the unit J K −1, which is equal to kg m 2 s −2 K −1, where the kilogram, metre and second are defined in terms of h, c and ∆ν Cs." [1]
The following table lists many specialized symbols commonly used in modern mathematics, ordered by their introduction date. The table can also be ordered alphabetically by clicking on the relevant header title.
In the International System of Units (SI), the unit of time is the second (symbol: s). It has been defined since 1967 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", and is an SI base unit. [12]