Mutuum

Mutuum is a contract in ancient Roman private law by which a lender transfers a fungible thing to a borrower for consumption with the obligation to return an equivalent quantity of the same kind. The common objects of mutuum are money and other fungible commodities such as grain, wine, or other goods that can be replaced by an identical quantity.

Under mutuum, ownership of the borrowed item passes to the borrower, who bears the risk of loss or deterioration and must repay the lender with an equivalent amount of the same kind. This distinguishes mutuum from commodatum (a loan for use), where the lender retains ownership and the borrower uses the item temporarily. The key obligation in mutuum is to return a quantity of the same kind and quality, not the exact physical item lent.

A typical mutuum involves a debt that arises from the transfer of fungible property; the borrower cannot demand the return of the original item and cannot substitute a different kind of thing unless the parties agree. If the borrower fails to repay the agreed quantity, the lender may sue for restoration of the same kind or its equivalent value at the time of repayment under the terms of the contract.

In modern private law, the concept survives in civil-law jurisdictions as the loan of money or other fungible goods to be repaid in kind. It is often contrasted with loans of use, and it remains a foundational distinction in the study of contracts for loans of fungible property. The term mutuum is retained in legal scholarship to describe this specific arrangement.