A physical quantity is a quantity in physics that can be measured. Or a physical quantity is a physical property that can be quantified. Examples of physical quantities are mass, amount of substance, length, time, temperature, electric current, light intensity, force, velocity, density, and many others. A physical quantity is always measured of natural non-living objects.
The foundation of physics rests upon physical quantities in term of which the laws of physics are expressed. Therefore, these quantities have to be measured accurately.