Riba al-nasi’ah (ربا النسيئة) is a type of riba (known as riba of postponement/ riba of delay) which arises from an unjustified increment in borrowing or lending, whether in cash or kind, over and above the principal amount (asl al-qardh). For example, a loan (qardh) of 1,000 currency unit (CU) may involve repayment of the principal amount (10,000 CU) along with payment of 100 CU after one calendar year. The 100 CU constitutes riba al-nasi’ah.

On the other hand, riba al-fadhl (ربا الفضل) (known as riba of excess or riba of surplus) originates when a ribawi item (ribawi commodity) is exchanged for the same item (commodity) in an unequal amount (even in spot transactions) and/ or a delay of the delivery of one of the items (commodities). For example,  the exchange of 20 grams of 21-karat gold for 25 grams of 19-karat gold gives rise to riba al-fadhl represented by the 5 grams of the lower quality gold.

Both types of riba represent an additional unjustified gain (impermissible gain) that is paid or surrendered by one party to another. Riba al-nasi’ah results from deferment of repayment in lending or borrowing transactions, while riba al-fadhl arises from the exchange of unequal amount of a ribawi item or spot-forward exchange of ribawi items.