Quotient of quantities of the same kind for different components within the same system.
Sources:
PAC, 1985, 57, 1299. 'Review of plasma deposition applications: preparation of optical waveguides' on page 1309 (https://doi.org/10.1351/pac198557091299)
PAC, 1996, 68, 957. 'Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)' on page 989 (https://doi.org/10.1351/pac199668040957)