Descriptores: MOND; gravedad modificada; inercia modificada; transformaciones de escala; invarianza. The basic principles that originated the Modified Newtonian Dynamics MOND, are shown, as well as a description of the fundamentals aspects of the theory: modification of gravity and modification of inertia. Also, it is considered the behaviour of the movement equations under space-temporal scale transformations of the movement equations, that is, transformations that have the form (t;~r) ! (‚t;~r). It was observed in this way that the MOND regime comes from the requirement of the invariance of the movement equations with respect to this transformations.