Rabb-Ul-Maal: The one who provides the finance in a Mudhaarabah agreement.
Rabi-al-Awwal: The third month of the Islamic calendar.
Radiallahu-Anha: May Allah be pleased with her.
Rak'at: One unit of a prayer.
Ramadhaan: Ninth month of the Islamic calendar.
Rasool: A messenger.
Rasulullah: Messenger of Allah (Prophet Muhammad).
Ratl: A measure used in Baghdad to weigh foodstuffs.
Riba: Literally means increase or addition and refers to the 'premium' that must be paid by the borrower to the lender along with the principal amount as a condition for the loaner OR an extension in its maturity. It is equivalent to interest.
Rikaaz: Buried treasure.
Rub-ul-Ushr: Quarter of a tenth.
Ruku: Ritual of bowing down in prayer.
Rukun: A principle.
Copied from 'THE ISLAMIC SCHOLAR'