density

Density tells how heavy something is, no matter its size. Just by looking at the weight numbers, one can get a better picture of what’s heavier and by how much? Even if a block of iron is the same size as a similarly sized piece of cotton, the iron is denser and, in fact, five times heavier than cotton. Density is the degree of compactness of a substance. I think this applies to bone density. The formula for density ρ when m the mass and V the volume are known is ρ  =  m/V.

Mass is a measure of the amount of matter in a substance or an object. The basic unit of mass is the kilogram (kg). For an approximate value in pounds, multiply the kg by 2.205.
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Volume is a measure of how much space an object or substance takes up. The basic unit of volume is the liter (l). For an approximate value in gallons, divide the l by 3.785.