Inertia

                The property of an object tending to maintain the state of rest or state of uniform  motion is referred to as the object's inertia.
                The more is the inertia, the stronger is this tendency in the presence of a force.
thus,
                "The mass of the object is a quantitative measure of its inertia".
we can says Newtons first law of motion called law of inertia.newtons first law is that
                 A body at rest will remain at rest, and a body moving uniform velocity will continue to do so, unless acted on by some unbalanced external force.This is also known as law of inertia.

Inertial Frame of Reference:

                    The frame of reference in which Newton's first law of motion holed, is known as inertial reference.A reference stationed on Earth is approximately an inertial frame of the body.

Inertia, Momentum and Impulse