Geometric SIMILARITY : It IMPLIES similarity of form. The model is a geometric reduction of the prototype and is accomplished by maintaining a fixed ratio for all homologous lengths between the model and the prototype.

Kinematic similarity : It implies similarity in motion. Kinematic similarity between a model and the prototype is obtained if the homologous moving particles have the same velocity ratio along geometrically SIMILAR paths. It INVOLVES the scale of TIME as well as length.

Dynamic similarity : It implies similarity in forces involved in motion.

Geometric similarity : It implies similarity of form. The model is a geometric reduction of the prototype and is accomplished by maintaining a fixed ratio for all homologous lengths between the model and the prototype.

Kinematic similarity : It implies similarity in motion. Kinematic similarity between a model and the prototype is obtained if the homologous moving particles have the same velocity ratio along geometrically similar paths. It involves the scale of time as well as length.

Dynamic similarity : It implies similarity in forces involved in motion.