According to Newton’s second law of motion, force is equal to mass times acceleration, meaning that mass and acceleration are inversely proportional. A constant force applied to two bodies of different masses leads to higher acceleration in the less massive body than in the more massive one.
Acceleration is the rate of change of velocity of an object due to a net force. This net force is the resultant force of all forces acting on the body at any given instant. The larger the magnitude of this net force, the larger the acceleration of the body. One of the definitions of mass is the resistance of a body to motion in general and acceleration in particular due to the application of force. The more massive a body is, the less it accelerates due to the application of force.
The concept of resistance to acceleration is closely tied to Newton’s first law and inertia, the tendency of a body to resist any change in its state of motion. The mass in Newton’s second law is often called the inertial mass, because it defines this tendency of a body to resist changes in motion. Moving a body from rest or stopping a moving body must always be accompanied by acceleration or deceleration regardless of how gradual or abrupt the change in motion.