Need help with the following: real risk-free rates, nominal risk-free rates, risk-free rates, and real rates of return.

[Enlighten_me]

1. Nominal risk- free rates
- I understand them to be the rates mentioned. However, this isn’t the real profit as there is still inflation to account for. Did I get it right or miss anything out? Feel free to add
2. Real risk- free rates
- The real profit.
3. Risk- free rates and Real rates of return
- As for these two, I am not sure if they are synonymous with any of the terms here or not. Please explain.