## Density

The density of a material is defined as its mass per unit volume. The symbol of density is ρ (the Greek letter rho). In some countries (for instance, in the United States), density is also defined as its weight per unit volume.

## Formula

Mathematically: Density = Mass Divided By Volume
$\rho = \frac{m}{V} \,$
where:
ρ (rho) is the density,
m is the mass,
V is the volume.
Different materials usually have different densities, so density is an important concept regarding buoyancy, metal purity and packaging.
In some cases density is expressed as the dimensionless quantities specific gravity (SG) or relative density (RD), in which case it is expressed in multiples of the density of some other standard material, usually water or air/gas.
font Wikipedia

## Featured Post

### IBSE about Light Pollution

Here is my presentation that happened in the Discover the Cosmos Conference (Volos, Greece - 2013). The presentation was an Inquiry Base...