What is the term for the amount of matter in an object?

The term that describes the amount of matter in an object is mass. Mass is a fundamental property of matter and is measured in kilograms or grams in the metric system. It reflects the quantity of matter present, regardless of the object's location, and does not change with the object's position in a gravitational field.

Weight, on the other hand, is the force exerted by gravity on that mass and varies depending on the strength of the gravitational field acting on the object. Volume refers to the space an object occupies, which is independent of the amount of matter within it. Density is a measure of how much mass is contained in a given volume, calculated as mass divided by volume. Therefore, mass directly defines the quantity of matter, making it the correct answer for this question.