""Doctors"" (dr.) can proceed to teach at universities as "universitair docent" (UD – assistant professor). With time, experience and/ or achievement, this can evolve to a position as "universitair hoofddocent" (UHD – associate professor). Officially an UHD still works under the supervision of a "hoogleraar", the head of the department and commonly a professor. However, this is not a given; it is also possible that a department is headed by a "plain" doctor, based on knowledge, achievement and expertise. The position of "hoogleraar" is the highest possible scientific position at a university and equivalent to the US "full" professor. The Dutch professor's title, noted as "prof. Jansen" or "professor Jansen", is connected to one's employment. This means that, should the professor leave the university, he or she also loses the privilege to use the title of professor. Retired professors are an exception and may continue to note the title in front of their name or use the title emeritus professor (em. prof.). People who switch to a non-university job lose their professor title and are only allowed to use the "dr." abbreviation.