Title: dimensionless quantities
Long Title: IUPAC Gold Book - dimensionless quantities
DOI: 10.1351/goldbook.D01742
Status: current

Definition
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, ...).

Related Terms
- absorbance: https://goldbook.iupac.org//terms/view/A00028
- power: https://goldbook.iupac.org//terms/view/P04792

Sources
- Green Book, 2nd ed., p. 77 (https://goldbook.iupac.org/files/pdf/green_book_2ed.pdf)
- PAC, 1996, 68, 957. 'Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)' on page 969 (https://doi.org/10.1351/pac199668040957)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/D01742/html
- json: https://goldbook.iupac.org/terms/view/D01742/json
- xml: https://goldbook.iupac.org/terms/view/D01742/xml

Citation: Citation: 'dimensionless quantities' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.D01742
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Disclaimer: The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.
Accessed: 2026-06-12T19:06:59+00:00