vehicle

https://doi.org/10.1351/goldbook.16185
Substance(s) used to formulate active ingredients for administration or use.
Note: In this context, it is a general term for solvents, suspending agents, etc.
Source:
PAC, 2007, 79, 1153. (Glossary of terms used in toxicology, 2nd edition (IUPAC Recommendations 2007)) on page 1332 [Terms] [Paper]