Repayment is the act of paying back money previously borrowed from a lender. Typically, the return of funds happens through periodic payments which include both principal and interest. Loans can usually also be fully paid in a lump sum at any time, though some contracts may include an early repayment fee.
Yes, it is true that caves are a type of island ecosystem according to the theory of island biogeography, since many caves at one point in time were in fact underwater.