[ginvite]

I was under the impression these terms were interchangeable and they meant the same thing? During lab pre-questions we are asked what is X used for ..When I put base/vehicle or for another question solvent/vehicle as my answer in lab I got point deductions.

[Arkcon]

It really does depend on the context.  You'll have to look at the definitions, maybe the ones you were given recently.  For example, "free base" means something different from "base composition."  And "solvent" may never mean "vehicle", or it might, but that may be specific jargon, but I wouldn't drink Guaifenesin in "solvent", even if someone said later, "the solvent is water plus emulsifier."  Or maybe I should, if I knew the jargon.