Quran Guides on Def of Riba

Financial Liability:
Qard (Loan) : to give anything in ownership of other by way of virtue - same or similar amount of that thing would be paid back on demand or at the settled time.
Dayn (Debt) : Incurred by way of trade or rent or any other credit transaction - ought to be returned at the settled time without any profit.
Verse 2: 279 guides that whatever is over and above the principal of loans or debts is Riba.