In general, a ratio of two quantities of the same kind, the numerator quantity applying to one @[email protected] (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 3 quantities: @[email protected], @[email protected], and @[email protected] (or @[email protected] equal to the @[email protected]).
Green Book, 2nd ed., p. 41 [Terms] [Book]
PAC, 1996, 68, 957. (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 974 [Terms] [Paper]