_____ is the amount of matter in an object.

The term you are looking for is mass. Mass is a fundamental property of matter and is defined as the quantity of matter that an object possesses. It is typically measured in units like kilograms (kg) or grams (g).

Mass is an intrinsic property, meaning it does not change regardless of the object's location in the universe, unlike weight, which can vary depending on the gravitational pull exerted on the object. In physics, mass plays a crucial role in determining the force exerted on an object when it is subjected to acceleration, as described by Newton's second law of motion: $F = ma$, where $F$ is the force applied, $m$ is the mass, and $a$ is the acceleration. Furthermore, while mass is a measure of matter, it also influences how objects interact in terms of gravitational attraction and inertia.