The relation between the "regular" frequency $f$ and the angular frequency $\omega$ ($\omega = 2\pi f$) is clear to me. However, every time I see "rotations per second" I really get confused as to what is meant there. How do I know whether the author means frequency or angular frequency, if "rotations per minute" can refer to both the frequency of rotations and the angular frequency of rotations as they both have the exact same unit $1 \over s$?
Before you mark this question as a duplicate, I've seen many questions regarding the differences between $f$ and $\omega $ but that's NOT what I'm asking here. I just want to know how to distinguish them when I come across a problem involving rotations and waves.