What are debt certificates that are purchased by an investor called?

I believe the answer is: Bond

By using bond, investor basically enter an agreement where they agree to loan a sum amount of money to the issuer in exchange for return plus interest in the future. In the issuer's financial records, bond would be treated similarly as a debt/liabilities.

Debt certificates that are purchased by an investor are called bonds. In finance, a bond is an instrument of indebtedness of the bond issuer to the holders.

They both used macro level approaches in their studies.

Explanation: just took the quiz of Ap ex