The correct statement about mass is:
Mass is the measure of the amount of matter in an object.
The other statements are incorrect:
- Mass is not measured in Newtons (N); Newtons are a unit of force.
- Mass itself is not a force but an intrinsic property of an object, while the gravitational force it experiences depends on its mass.
- The mass of an object is a constant value and does not vary under normal conditions.