Riba.

Riba:
The word Riba means excess, increase or addition. According to Shariah terminology, it implies any excess compensation without due consideration.
(This definition of Riba is derieved from Holy Quran and is unanimously accepted by all Islamic scholars.

Classification
                   There are two types of Riba, idetified to date by the scholars namely "Riba An Nasiyah" and Riba Al Fadl".