Nuveen Senior Income Fund is a diversified, closed-end management investment fund. The Fund's investment objective is to achieve a high level of current income, consistent with capital preservation by investing primarily in adjustable rate United States dollar-denominated secured Senior Loans. The Fund focuses on investing in industries, including media, software, food and staples retailing, health care equipment and supplies, and hotels restaurants and leisure. The Fund invests at least 80% of its managed assets in adjustable rate senior secured loans. Up to 20% may include United States dollar denominated senior loans of non-United States borrowers, senior loans that are not secured, other debt securities, and equity securities and warrants. The Fund's investment advisor is Nuveen Fund Advisors, LLC. The Fund's investment manager is Symphony Asset Management, LLC.