What is the difference between "researcher" and "research scientist"? I often see them used interchangeably and therefore wonder whether they are synonymous.
A research scientist is a scientist who is engaged in the process of experimentation and investigation (ie doing research). If a scientist is not a research scientist they may be a teacher, or an engineer, for example. Research scientists will normally hold a PhD, or equivalent.
A researcher is not necessarily a scientist at all. For example, politicians will employ researchers to investigate political matters. Researchers investigate stories for journalists. In this context, researchers are typically a quite low level position, that may even be taken by an intern.
So while all research scientists are researchers, not all researchers are scientists.