Literally, riba (ربا) denotes the meanings of excess, increase, growth, accretion and expansion.

Technically, it refers to:

• Every excess in return or compensation (iwadh) for which no equal value or equivalent counter-value is paid.
• A prefixed excess or surplus over and above a loan (qardh) as stipulated in a contract (aqd) or according to customary practices (urf) in relation to a given period of time.
• A mandatory (stipulated) increase in value in an amount being lent out.

Riba comes in many forms and guises including:

• Riba al-nasi’ah (riba of deferment/ time factor).
• Riba al-fadhl/ riba al-fadl (riba of excess).
• Riba al-qardh/ riba al-qard (riba of loans).
• Riba al-sunnah (riba mentioned in sunnah).
• Riba al-Quran (riba mentioned in Quran).
• Riba al-buyu (riba of sales or riba associated with a sale).
• Riba al-duyun (riba of debts).
• Riba al-jahiliyyah (pre-Islam riba).

For more on riba, see: meaning of riba.