Mass refers to the amount of matter an object contains. It is a measure of the inertia or resistance to changes in motion.
Weight is the force exerted on an object due to gravity. It depends on both the mass of the object and the acceleration due to gravity.
Inertia is the tendency of an object to resist changes in its state of motion. Objects with greater mass have greater inertia.
Density: Density is a measure of how much mass is contained within a given volume. It can be calculated by dividing an object's mass by its volume.