 For example, in the case supposed, they may agree that the sale of the car is to take place only if the car is approved of by Rodney, or they may agree that the R100,000 is payable in monthly instalments of R10,000.These modifications of the contract, it will be seen directly, constitute either ‘conditions’ or ‘terms of performance’.According to the Roman-Dutch classification, then, terms may be classified as "essentialia", "naturalia" or "incidentalia"