In V=pi*D*n formula what does the ( v & D ) refer to ??? it is in cutting conditions in turning !

V= velocity
pi = 3.14....
D = Diameter of a circle
n = frequency = revolutions / second

So:
Since the circumference of the circle is = pi*D
the formula will offer you the velocity an object moves around a center (in m/sec or ft/sec) as a function of the aforementioned quantities.

Velocity
Distance