What is usury [riba] linguistically and terminologically?

Linguistically, riba means increase, and from this comes the Almighty’s saying: (But when We send down thereon water, it stirs and swells). Technically, the Hanafis defined it as: an excess devoid of consideration, according to a legal standard, stipulated for one of the two contracting parties in an exchange. The Shafi’is defined it as: a contract over consideration with a specific, unknown equality in the legal standard at the time of the contract, or with a delay in both substitutes or one of them. The Hanbalis defined it as: an excess in certain things and a delay in certain things, specifically pertaining to things regarding which the Sharia has forbidden riba.