This all assumes an exponent of n = 4 {\displaystyle n=4\,\!} which is appropriate for the uniform (homogeneous) nucleation in three dimensions. Thin films, for example, may be effectively two-dimensional, in which case if nucleation is again uniform the exponent n = 3 {\displaystyle n=3\,\!} . In general, for uniform nucleation and growth, n = D + 1 {\displaystyle n=D+1\,\!} , for D {\displaystyle D\,\!} the dimensionality of space in which crystallization occurs.