A measure of how much matter is in an object.
This gold bar has a mass of 1 kilogram (about 2.2 pounds).
Unlike weight, which depends on gravity, mass remains constant regardless of location.
On Earth we often measure mass by weighing an object, because gravity is relatively constant here. But since weight is the force of gravity acting on mass, your weight on the Moon is less than here on Earth while your mass stays the same.
Mass is usually measured in:
• grams, kilograms and tonnes in Metric,
• ounces, pounds and tons in US units.
See: Weight