It is a measurement of the amount of a substance contained in a certain volume. The density of any solid is the mass of the object divided by its volume.

The mass of a bag of sugar ... as it is a large number of relatively small units of measure. In this case it would be more helpful to convert that measure into kilometres. There are 1000 metres ...

In prehistoric times, not much needed to be measured. You ate what you found and lived where you could. The […] ...

Metric measurements — also known as ... iridium that was originally used to define mass. Today, after decades of work, each of those units is instead defined by an invariant physical property.