Mass

A measure of how much matter is in an object.

This gold bar is quite small but weighs 1 kilogram (about 2.2 pounds), so it contains a lot of matter.

Mass is commonly measured by how much something weighs. But weight can change depending on where you are (such as in a moving elevator or on the moon) while the mass stays the same.

It is measured in grams, kilograms and, tonnes (Metric) or ounces and pounds (US units)