Title: fraction
Long Title: IUPAC Gold Book - fraction
DOI: 10.1351/goldbook.F02494
Status: current

Definition
In general, a ratio of two quantities of the same kind, the numerator quantity applying to one constituent (or part) of the system and the denominator to the sum of quantities for all constituents (parts) of the system. When applied to mixtures fractions represent a group of three quantities: mass fraction, volume fraction, and amount fraction (or amount fraction equal to the number fraction).

Related Terms
- amount fraction: https://goldbook.iupac.org//terms/view/A00296
- constituent: https://goldbook.iupac.org//terms/view/C01281
- mass fraction: https://goldbook.iupac.org//terms/view/M03722
- number fraction: https://goldbook.iupac.org//terms/view/N04265
- volume fraction: https://goldbook.iupac.org//terms/view/V06643

Sources
- Green Book, 2nd ed., p. 41 (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 974 (https://doi.org/10.1351/pac199668040957)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/F02494/html
- json: https://goldbook.iupac.org/terms/view/F02494/json
- xml: https://goldbook.iupac.org/terms/view/F02494/xml

Citation: Citation: 'fraction' 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.F02494
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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: 2026-04-24T20:58:46+00:00