Modified Newtonian dynamics proposed that gravitational field needs modifications when the field strength $g$ is weaker than a critical value $g_0$. This has been shown to be a good candidate as an alternative to cosmic dark matter. There is another way to look at this theory as a length scale dependent theory. One will show that modification of the Newtonian field strength depends on the mass distribution and the coordinate scale of the system. It is useful to separate the effective gravitation field $g(r)$ into a small scale (or short-distance)$g_s$ field and a large scale (or a long-distance) $g_l$ field that should be helpful for a better understanding of the underlying physics. The effective potential is also derived.

9 pages, 8 figures