Nuveen Senior Income Fund's investment objective is to achieve a high level of current income, consistent with capital preservation by investing primarily in adjustable rate U.S. dollar-denominated secured Senior Loans. The Fund invests at least 80% of its managed assets in adjustable rate senior secured loans. Up to 20% may include U.S. dollar denominated senior loans of non-U.S. borrowers, senior loans that are not secured, other debt securities, and equity securities and warrants. The Fund uses leverage.