coefficient

https://doi.org/10.1351/goldbook.C01124
Proportionality constant between two quantities of different dimension.
Source:
ISO 31-0: 1992 [Terms] [Book]
See also:
PAC, 1996, 68, 957. (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 966 [Terms] [Paper]