whats the difference
reinvestment risk is the risk that you will have to reinvest interest payments or capital repayments at a lower rate. Repayment risk is the risk that there will be capital repayments, which then expose you to reinvestment risk.
when a person pays a portion of loan principal back, you are on the hook to find a similar yield.
To add to those responses, prepayment risk is the risk associated with the bond holder having an option to prepay the principal thus exposing you to reinvestment risk.