So far, in our discussion, we have assumed the existence of an inertial reference frame and all the experiments and theories have been developed for inertial reference frames. Reality seems to be otherwise. In fact, there is no inertial reference frame. Our laboratories are situated on the earth and any reference frame attached to the earth is not inertial reference frame, owing to its revolution around the sun and rotation about its own axis. The earth has translational motion which is not uniform and rotational motion. It is therefore doubly non-inertial. However, we cannot discard everything developed so far. We have already discussed with suitable reasoning that for practical purposes, the earth may be taken as inertial reference frame. Nevertheless, it is worth to discuss about the motions in non-inertial reference frames. An inertial reference frame moves with constant linear velocity. Thus, the deviation from non-inertial can be in two ways: (i) reference frame is moving with accelerated linear velocity and (ii) reference frame is moving with angular velocity. We shall handle the anomaly in two steps. First, we shall see how to make corrections when our reference frame is moving with linear acceleration with respect to an inertial reference frame. Next, we shall account for corrections when our reference frame is rotating with respect to an inertial reference frame.