docent

dosentti instructive Instructive; that teaches.
A teacher or lecturer at some American colleges or universities.
2006, Thomas Pynchon, Against the Day, Vintage 2007, p. 1212:

Zermelo had been a docent at Göttingen when Kit was there and, like Russell, had been preoccupied with the set of all sets that are not members of themselves.

The docent greeted the visitors and welcomed them to the Louvre.