A more thorough explanation:

Definition: Fructus civiles (pronounced fruhk-tuhs si-vil-eez) is a Latin term used in Roman and civil law to refer to income received from another person for the use or enjoyment of a thing, such as real property or loaned money. This income can come in the form of rent or interest.

Examples: An example of fructus civiles would be the rent paid by a tenant to a landlord for the use of an apartment. Another example would be the interest paid by a borrower to a lender for a loan.

Fructus civiles can also include earnings from slaves and minerals, as was the case in Roman law.

These examples illustrate how fructus civiles refers to the income received from the use or enjoyment of a thing, rather than the thing itself. In other words, the landlord does not own the apartment, but rather receives income from the tenant's use of it. Similarly, the lender does not own the money borrowed, but rather receives income from the borrower's use of it.