りそく利息risoku
1.

A monetary compensation received by a lender from a borrower, calculated as a percentage of the principal amount over time.

2.

A commonly used term referring to the earnings generated as a result of lending money, distinct from the original sum loaned.

Example:

彼は利息を付けて借金払いをした。

むりそく無利息murisoku
1.

A condition in which no additional charges are applied to the principal amount over time, often associated with loans or deposits.

2.

A scenario where an account or financial transaction does not accrue any interest, resulting in the original sum remaining unchanged.

3.

A financial state where money is lent or borrowed without the expectation of earning or paying any extra amount in interest.