Number
A basic SI number is a float, such as 12345.67891
. The decimal marker can also be a comma, such as 12345,67891
. For readable, a thin space is also allowed, such as 12 345.678 91
. Exponentiation is specified with the superscipt numbers; 3²
is equivalent to 9
.
A precentage is specified with the percent sign. 0.25 %
is equivalent to 0.0025
.
An uncertain value is specified with the left parenthesis and right parenthesis symbols, such as 12 345.678 91(5)
and is equivalent to 12345.67891±0.00005
.
Multiplication is specified with the multiplication sign, such as 1.234 567 891(5) × 10⁴
and is equivalent to 12 345.678 91 ± 0.000 05
.
ASCII Number
The SI representation of a number requires Unicode code points outside of the ASCII characters. To make life easier for programmers the following relaxations are allowed:
- Any white space character can be used for a thin space
*
can be used for a multiplication sign^
or**
can be use for exponentiation
For example, 1.234 567 891(5) * 10**4
is equivalent to 12345.67891±0.00005
Quantity
A SI Quantity consists of a number and a unit. If not specified, the number defaults to 1
. The unit is a defined ISO-80000 symbol or a symbolic expression.
Any of the following expressions can be used to define watt per square metre steradian:
W/(m² sr)
m² m⁻² kg s⁻³
kg s⁻³