Quantities of dimension one, or numerical quantities, are numbers which may be integers
(or exceptionally half-integers) when obtained by counting (e.g. number of molecules,
quantum numbers, ...), rational numbers such as ratios, factors and fractions when
obtained as ratios of two quantities of the same kind or real numbers when obtained
by taking logarithms (e.g. absorbance, power levels, ...).

Source:

PAC, 1996, *68*, 957*
(Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations
1996))
* on page 969