What is the best way (terminology) for a postdoc (PDRA) to refer to their 'boss'/'supervisor'? A postdoc, postdoctoral research assistant in a university on a contract has a supervisor or a boss. They may not be the PI on the grant which pays the salary as it may contain other universities as well. 

In conversation and in email, what is the best term to use for your postdoc boss? Something doesn't seem correct with the term boss or manager, or even supervisor.
I've heard "supervisor", "advisor" and "mentor".  They can be clarified as "postdoc advisor", etc, to avoid confusion with a Ph.D. advisor.

There's also the simpler "I work with Professor Smith."