# What is matter and what is mass?

In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. (Wiki)

Fair enough, so what is mass?

Mass is the quantity of matter in a physical body. (Wiki)

Ok, these definitions are cyclic. Can someone explain what the two are without relying on the other to explain it? Is matter even something that has a precise definition in physics or is it more like a word to describe some intuitive properties of some things?

• The first one seems ok but mass can be thought of how much matter there is in total. If you have an ice cube and it has a mass of 5 grams, and then you evaporate it, then that water vapor will still have 5 grams of mass (it has not gone away). Jan 30 at 21:40
• Alternatively, mass can be thought of as a property of matter that creates inertia for matter. Jan 30 at 21:52
• Similar - What exactly is mass?, Definition of mass Jan 30 at 22:31

More simply, mass can be operationally defined as the quantity measured by a scale. It can also be theoretically defined as the quantity $$m$$ in the expression $$m^2 c^2=E^2/c^2-p^2$$. This is a nice theoretical definition because it allows you to determine the mass of things that you cannot put on a scale.