What is the term for the amount of matter in an object and its resistance to change in motion?

The term that describes the amount of matter in an object and its resistance to changes in motion is mass. Mass is a fundamental property of an object that quantifies the amount of material present; it is a scalar quantity and is typically measured in kilograms.

In addition to being a measure of matter, mass is directly related to inertia, which is the property of an object that resists changes to its state of motion. While inertia is often discussed in the context of an object's resistance to movement, it is intrinsically connected to mass since greater mass results in greater inertia.

Weight, on the other hand, is the force exerted by gravity on an object and varies depending on the gravitational field strength. Volume refers to the space an object occupies and does not relate directly to the matter or the resistance to changes in motion. Therefore, mass is the appropriate term for describing both the quantity of matter and the associated resistance to changes in motion.