A 'classical' percentage is a number x such as 0 <= x <= 100
probability
union
A 'classical' probability is a number x such as 0 <= x <= 1. Other types of
probabilities (e.g. exotic and negative probabilities) are not included in
this definition.
proper-fraction
union
A fraction that is less than or equals 1
scalar
union
A scalar is a dimensionless and unitless value. Please refer to the si-unit
system if the scalar has a meaning. This is a variable, but by defining it as a
scalar, it is explicitly not a vector coordinate.