What is the measurement of the amount of matter in an object called?

The measurement of the amount of matter in an object is referred to as mass. Mass is a fundamental property of matter and denotes the quantity of matter contained within an object, typically measured in kilograms or grams. It's important to understand that mass is distinct from weight; weight is a measure of the force exerted by gravity on an object and can vary depending on the gravitational field strength, while mass remains constant regardless of location.

Volume measures the space an object occupies, and density is a property that relates mass to volume, indicating how much mass is present in a given volume of space. Hence, the definition clearly aligns with mass being the measurement of matter, making it the correct answer.