Geometric modelling is an integral part of any Computer-Aided-Design (CAD) system. Integration of geometric modelling; computer graphics along with design principles develops CAD tools. Therefore, in this unit, a brief treatment of representation of curves is presented. Curve representation in parametric form would increase the graphical representation of curves apart from ease of computation. Synthetic forms of curves such like Hermite cubic B-Splines, Bezier, B-Splines and Nurbs have been extensively used to represent several practical situations being modelled in CAD systems. A detailed treatment of these curves is presented. The features of Wire-frame models and its applications are also discussed.