What is the meaning of the various postdoctoral job descriptions in the US? As somebody who wasn't born or raised in North America, is there a schematic explanation what those various terms are supposed to be mean? Does it differ between the types of institutions? Are there specific fixed meanings to keywords such as

Assistant
Associate
Visitor
Fellow
Research


If there are not specific meanings, how do committees decide what to call a position?
As Jon Custer mentioned in the comments, there are no standards whatsoever, however generally speaking:

&quot;Visiting&quot; is a short-term position (I've never seen a post-doc with this title), probably even shorter than a usual postdoc, probably 9 or 12 months.

A &quot;fellow&quot; is usually a prestigious assignment, it may be a  university, college, or departmental soft-money position. For example, my university has &quot;President's Fellows&quot; although I'm not sure if they are funded specially or if that's just an award. However, nothing stops anyone from calling anything a &quot;fellow.&quot;

An &quot;associate&quot; professor outranks an &quot;assistant.&quot; However, I do not think there is any meaningful difference between &quot;postdoctoral research assistants&quot; and &quot;postdoctoral research associates.&quot; One doesn't outrank the other. Probably, people just try to avoid using &quot;research assistant,&quot; since that somewhat connotes an junior position.